# The 100 largest cybersecurity companies in the United Kingdom
Tamtam tracks 549 cybersecurity companies headquartered in the United Kingdom. This list ranks the 100 largest by number of employees on LinkedIn, led by BT Group, BAE Systems and SCC. Their median headcount is 563. Half of them were founded in 2002 or later. The most common headquarters are London (38), Manchester (5) and Birmingham (3).
This selection of large cybersecurity companies in the United Kingdom includes major players in telecommunications and defense, alongside specialized IT and software firms. BT Group, for example, is a global communications services company, while BAE Systems provides advanced technology-led defense and security solutions. Sophos is a global cybersecurity leader offering advanced solutions, and Darktrace specializes in AI cybersecurity platforms.
A notable pattern is the concentration of headquarters in London, with several other significant companies based in cities like Birmingham, Abingdon, and Cambridge. The companies listed range from established entities like SCC, founded in 1975, to younger firms such as TryHackMe, established in 2018.
π¬π§ United Kingdom Β· 100 companies Β· Updated Nov 12, 2026
| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [BT Group](https://www.tamtam.ai/c/bt-group) (bt.com)
A global communications services company connecting people through technology to address challenges like the pandemic, climate change, and cyber security | Telecommunications | π¬π§ London | 73,712 | |
| 2 | [BAE Systems](https://www.tamtam.ai/c/bae-systems) (baesystems.com)
The company provides advanced technology-led defense, aerospace, and security solutions, with a skilled workforce in over 40 countries, focusing on innovation and long-term commitment | Defense and Space Manufacturing | π¬π§ London | 55,143 | 1999 |
| 3 | [SCC](https://www.tamtam.ai/c/scc) (scc.com)
SCC is a leading IT group in Europe, providing limitless IT solutions, cyber security services, digital workplace solutions, and hybrid infrastructure services | IT Services and IT Consulting | π¬π§ Birmingham | 8,687 | 1975 |
| 4 | [Vodafone Business](https://www.tamtam.ai/c/vodafone-business) (vodafone.com)
Providing mobile, fixed, unified communications, IoT, cloud, and security services to businesses globally, regionally, and locally. | Telecommunications | π¬π§ London | 8,100 | |
| 5 | [QinetiQ](https://www.tamtam.ai/c/qinetiq) (qinetiq.com)
Integrated global defence and security company focused on mission-led innovation, testing technologies, and enabling customers to deploy enhanced capabilities for protecting lives. | Defense and Space Manufacturing | π¬π§ Farnborough | 5,512 | |
| 6 | [Sophos](https://www.tamtam.ai/c/sophos) (sophos.com)
A global cybersecurity leader offering advanced solutions, managed services, and a broad portfolio of technologies to protect organizations from cyberattacks worldwide | Software Development | π¬π§ Abingdon | 5,498 | 1985 |
| 7 | [Logicalis](https://www.tamtam.ai/c/logicalis) (logicalis.com)
A global technology service provider helping organizations succeed in a digital-first world through cloud, connectivity, collaboration, and security solutions | IT Services and IT Consulting | π¬π§ Maidenhead | 4,868 | 1998 |
| 8 | [Noventiq](https://www.tamtam.ai/c/noventiq) (noventiq.com)
A global digital transformation and cybersecurity solutions provider connecting 80,000+ organizations, with a diverse portfolio and active M&A strategy for growth | IT Services and IT Consulting | π¬π§ London | 3,941 | |
| 9 | [TryHackMe](https://www.tamtam.ai/c/tryhackme) (tryhackme.com)
It simplifies learning and teaching Cybersecurity through prebuilt courses and cloud-hosted virtual machines, ideal for CTFs, workshops, and training. | Computer and Network Security | π¬π§ London | 3,445 | 2018 |
| 10 | [Micro Focus](https://www.tamtam.ai/c/micro-focus) (opentext.com)
Provides AI, analytics, application development, modernization, and digital operations technologies to support digital transformation and smarter work processes. | IT Services and IT Consulting | π¬π§ Newbury | 3,383 | |
| 11 | [BAE Systems Digital Intelligence](https://www.tamtam.ai/c/bae-systems-digital-intelligence) (baesystems.com)
A global team of over 4,500 experts in digital, cyber, and intelligence, collaborating to collect and analyze complex data for governments and businesses | Defense and Space Manufacturing | π¬π§ Guildford | 3,252 | 1971 |
| 12 | [LRQA](https://www.tamtam.ai/c/lrqa) (lrqa.com)
The company provides certification, brand assurance, food safety, cybersecurity, inspection, and training services to help clients build safer, more sustainable businesses | International Trade and Development | π¬π§ Birmingham | 3,169 | |
| 13 | [Claranet](https://www.tamtam.ai/c/claranet) (claranet.com)
A global technology services provider offering managed services, professional services, and training in Cloud, Networks, Cyber Security, and Workplace technologies since 1996 | IT Services and IT Consulting | π¬π§ London | 3,073 | 1996 |
| 14 | [Quantum Security Agency](https://www.tamtam.ai/c/quantum-security-agency) (org.uk)
Specialized restaurant marketing agency offering solutions to help restaurants thrive through social media management, content marketing, websites, and other marketing services | Software Development | π¬π§ London | 2,842 | 2007 |
| 15 | [Darktrace](https://www.tamtam.ai/c/darktrace) (darktrace.com)
AI cybersecurity platform learns unique data, detects threats, and intervenes against attacks, protecting organizations worldwide from cyber-threats. | Computer and Network Security | π¬π§ Cambridge | 2,632 | 2013 |
| 16 | [NCC Group](https://www.tamtam.ai/c/ncc-group) (nccgroupplc.com)
Cybersecurity firm advising global organizations on protecting data and systems, with expertise in assessing, mitigating, and responding to cyber threats Offices worldwide | IT Services and IT Consulting | π¬π§ Manchester | 2,617 | 1999 |
| 17 | [Gamma](https://www.tamtam.ai/c/gamma) (gammagroup.co)
Gamma is a leading supplier of Unified Communications services in the UK, Germany, Spain, and Benelux, offering robust solutions for communication and collaboration | Telecommunications | π¬π§ London | 2,588 | 2002 |
| 18 | [Mimecast](https://www.tamtam.ai/c/mimecast) (mimecast.com)
Protects humans, data, and AI agents through a unified platform, securing the workforce and their interactions with AI from cyberattacks. | Computer and Network Security | π¬π§ London | 2,396 | 2003 |
| 19 | [Hack The Box](https://www.tamtam.ai/c/hack-the-box) (hackthebox.com)
Leading platform enhancing organizational cyber resilience, battle-testing and upskilling humans and AI agents through real-world scenarios and gamified labs. | Computer and Network Security | π¬π§ Folkestone | 2,309 | 2017 |
| 20 | [Hardware](https://www.tamtam.ai/c/hardware) (kubus.com)
A hardware company formed in 2003 is now Kubus Group Limited Follow on LinkedIn for company updates, employee information, and career opportunities | IT Services and IT Consulting | π¬π§ Cirencester | 1,667 | 2003 |
| 21 | [MTI](https://www.tamtam.ai/c/mti-staines-upon-thames) (mti.com)
Provides comprehensive cybersecurity and data centre technology solutions, managed services, and consulting to support secure, compliant IT infrastructure management. | IT Services and IT Consulting | π¬π§ Staines-upon-Thames | 1,660 | 1987 |
| 22 | [Synamedia](https://www.tamtam.ai/c/synamedia) (synamedia.com)
A trusted provider of video protection, enrichment, and delivery solutions, offering cloud products for launching, monetizing, and scaling services quickly | Broadcast Media Production and Distribution | π¬π§ Weybridge | 1,437 | 2018 |
| 23 | [GBG Plc](https://www.tamtam.ai/c/gbg-plc) (gbg.com)
Combines global data and innovative technology to verify identities and locations, protecting against digital crime and supporting business growth. | IT Services and IT Consulting | π¬π§ Chester | 1,358 | 1989 |
| 24 | [Jisc](https://www.tamtam.ai/c/jisc) (jisc.ac.uk)
National research infrastructure providing high-speed connectivity, cyber security, and technology solutions to UK universities and schools through shared services and digital data tools. | Education | π¬π§ Bristol | 1,333 | |
| 25 | [Focus Group](https://www.tamtam.ai/c/focus-group) (focusgroup.co.uk)
Provides essential business technology, including telecoms, IT, connectivity, mobile, cyber security, and energy solutions for various organizations, ensuring optimized and secure operations. | Technology, Information and Internet | π¬π§ Shoreham-by-Sea | 1,315 | 2003 |
| 26 | [MASS](https://www.tamtam.ai/c/mass) (mass.co.uk)
A dynamic technology company within the Cohort plc group, specializing in electronic warfare support, cyber security, IT managed services, and data management | Defense and Space Manufacturing | π¬π§ St Neots | 1,294 | |
| 27 | [Wavenet](https://www.tamtam.ai/c/wavenet) (wavenet.co.uk)
A UK-based company providing unified communications, business telephony, and Cyber Security solutions to help businesses overcome real challenges and achieve brilliance | Technology, Information and Internet | π¬π§ Solihull | 1,284 | 2000 |
| 28 | [First Technology UK](https://www.tamtam.ai/c/first-technology-uk) (first-technology.co.uk)
A group of companies providing IT products and services to help organizations navigate technology challenges and achieve their business outcomes | IT Services and IT Consulting | π¬π§ Pangbourne | 1,224 | 1982 |
| 29 | [Cybersecurity](https://www.tamtam.ai/c/cybersecurity) (org.uk)
Cybersecurity experts providing incident response training, social engineering defense, vulnerability scanning, threat hunting, API testing, mobile app security, privacy compliance, user awareness training, and more | Computer and Network Security | π¬π§ London | 1,209 | 2017 |
| 30 | [DNS](https://www.tamtam.ai/c/dns-edinburgh) (dns.co.uk)
A global security services provider recently acquired a UK-based company specializing in managed security services and consulting for clients | IT Services and IT Consulting | π¬π§ Edinburgh | 1,173 | 1999 |
| 31 | [Reed Business Information](https://www.tamtam.ai/c/reed-business-information) (risk.lexisnexis.com)
Provides innovative data analytics, decision tools, and management services across industries to reduce risk, ensure compliance, and improve operations. | IT Services and IT Consulting | π¬π§ | 1,061 | |
| 32 | [ANS Group](https://www.tamtam.ai/c/ans-group) (ans.co.uk)
Providing accessible, affordable enterprise-grade technology and digital transformation solutions to businesses of all sizes, enabling growth and innovation. | IT Services and IT Consulting | π¬π§ Manchester | 975 | 1996 |
| 33 | [Maintel](https://www.tamtam.ai/c/maintel) (maintel.co.uk)
Provider of cloud communications and managed services, specializing in digital transformation for public and private sectors Delivering digital workplace, customer experience, and secure connectivity solutions globally | Telecommunications | π¬π§ London | 946 | 1991 |
| 34 | [Node4](https://www.tamtam.ai/c/node4) (node4.co.uk)
Node4 specializes in providing a wide range of tech solutions and managed services to help organizations achieve their strategic goals through digital transformation | IT Services and IT Consulting | π¬π§ Derby | 933 | 2004 |
| 35 | [Roke](https://www.tamtam.ai/c/roke) (roke.co.uk)
Engineering advanced data, communication, AI, and sensor technologies for national security, defense, and commercial clients to solve complex challenges. | Defense and Space Manufacturing | π¬π§ Romsey | 900 | 1956 |
| 36 | [Dimension Data UKI](https://www.tamtam.ai/c/dimension-data-uki) (services.global.ntt)
This company helps organizations achieve their goals through digital infrastructure, hybrid cloud, workspaces, and cybersecurity, empowering businesses to excel and grow with ICT solutions | IT Services and IT Consulting | π¬π§ Fleet | 895 | 1983 |
| 37 | [Bell Integration](https://www.tamtam.ai/c/bell-integration) (bell-integration.com)
Provides technology consultation and managed services enabling organizations to transform IT capabilities, enhancing productivity, and cost efficiency. Specializes in IT services and infrastructure. | IT Services and IT Consulting | π¬π§ Portsmouth | 885 | 1996 |
| 38 | [Bytes Software Services](https://www.tamtam.ai/c/bytes-software-services) (bytes.co.uk)
Provider of IT solutions including cloud, security, AI, data management, licensing, training, deployment, and managed services for diverse sectors. | IT Services and IT Consulting | π¬π§ Leatherhead | 868 | 1982 |
| 39 | [Arrow Business Communications](https://www.tamtam.ai/c/arrow-business-communications) (aro.tech)
Provides cloud, collaboration, and sustainability IT solutions to major UK clients including FTSE100 companies, law firms, universities, NHS, and emergency services. | Telecommunications | π¬π§ Godalming | 836 | |
| 40 | [GCX](https://www.tamtam.ai/c/gcx) (gcxworld.com)
Network services enabling digital transformation through managed SD-WAN, hybrid networks, and extensive subsea cloud connectivity across emerging markets and Asia. | Telecommunications | π¬π§ London | 810 | 1988 |
| 41 | [Kerv](https://www.tamtam.ai/c/kerv) (kerv.com)
Kerv is a purpose-driven cloud and digital services organization providing enterprise software, consulting, networking, security, and digital transformation services across key industries | IT Services and IT Consulting | π¬π§ London | 782 | 2020 |
| 42 | [Nasstar](https://www.tamtam.ai/c/nasstar) (nasstar.com)
specialise in managed technology services including cloud optimisation, application modernisation, networking, security, and consultative implementation for business success | IT Services and IT Consulting | π¬π§ Wakefield | 755 | 1998 |
| 43 | [Beyond](https://www.tamtam.ai/c/beyond) (bynd.com)
A design agency focused on enhancing customer experiences through strategy, technology, and design, serving diverse clients globally with a remote-first workforce | IT Services and IT Consulting | π¬π§ London | 752 | 2010 |
| 44 | [Zenzero](https://www.tamtam.ai/c/zenzero) (zenzero.co.uk)
Design tailored IT infrastructure solutions using proven technologies to optimize client operations and maximize value from resources. | IT Services and IT Consulting | π¬π§ London | 688 | 2004 |
| 45 | [Options Technology](https://www.tamtam.ai/c/options-technology) (options-it.com)
Provides global financial technology solutions specializing in banking and trading infrastructure, integrating high-performance networking, cloud, security, and AI technologies. | IT Services and IT Consulting | π¬π§ London | 641 | 1993 |
| 46 | [Acora - IT, Cyber & AI](https://www.tamtam.ai/c/acora-it-cyber-and-ai) (acora.com)
UK-based company offering IT support, cybersecurity, applications, data management, and cloud solutions to protect and optimize business technology. | IT Services and IT Consulting | π¬π§ Burgess Hill | 639 | 1989 |
| 47 | [PXC](https://www.tamtam.ai/c/pxc) (pxc.co.uk)
Leading UK wholesale provider of connectivity, voice, cloud, and security solutions with a robust network, offering tailored support for business growth and success | Telecommunications | π¬π§ Manchester | 604 | |
| 48 | [Redcentric](https://www.tamtam.ai/c/redcentric) (redcentricplc.com)
A managed service provider delivering network, cloud, and collaboration solutions to help public and private sector organizations succeed with agile and assured services | IT Services and IT Consulting | π¬π§ Harrogate | 602 | 1997 |
| 49 | [boxxe](https://www.tamtam.ai/c/boxxe) (boxxe.com)
Provider of hardware, software, and managed IT services delivering flexible technology solutions to enhance productivity, security, and operational efficiency. | IT Services and IT Consulting | π¬π§ Hemel Hempstead | 578 | 1987 |
| 50 | [Positive Technologies](https://www.tamtam.ai/c/positive-technologies) (ptsecurity.com)
A leader in cybersecurity solutions, offering innovative products and services to detect and neutralize risks in corporate IT infrastructure globally | Computer and Network Security | π¬π§ Moscow | 563 | |
| 51 | [TSG](https://www.tamtam.ai/c/tsg) (tsg.com)
TSG is a leading UK IT company providing comprehensive technology solutions and support including IT infrastructure, software, telecoms, broadband, and cloud computing | IT Services and IT Consulting | π¬π§ Gateshead | 561 | 2003 |
| 52 | [TelefΓ³nica Tech (EN)](https://www.tamtam.ai/c/telefonica-tech-en) (telefonicatech.uk)
Specialist provider of integrated technology solutions including cybersecurity, cloud, data, AI, business applications, and digital workplace services. | IT Services and IT Consulting | π¬π§ London | 557 | |
| 53 | [Fortray Global Service Limited](https://www.tamtam.ai/c/fortray-global-service-limited) (fortray.com)
Provides services for digital transformation, cybersecurity, cloud, and managed IT. Also develops talent through tech and AI bootcamps for various digital skills. | IT Services and IT Consulting | π¬π§ London | 547 | 2011 |
| 54 | [Methods](https://www.tamtam.ai/c/methods) (methods.co.uk)
Digital transformation partner for UK public sector, specializing in helping government agencies improve services through innovative technology solutions and cost-saving strategies | IT Services and IT Consulting | π¬π§ London | 534 | 1990 |
| 55 | [SecurityHQ](https://www.tamtam.ai/c/securityhq) (securityhq.com)
It is a global cybersecurity company providing tailored solutions to enhance security posture and maximize cybersecurity investment for organizations. | IT Services and IT Consulting | π¬π§ London | 503 | 2003 |
| 56 | [Resillion](https://www.tamtam.ai/c/resillion) (resillion.com)
A global leader in quality engineering, testing, and cyber security services, providing end-to-end digital testing solutions with a dedication to success and cutting-edge technology | IT Services and IT Consulting | π¬π§ London | 479 | |
| 57 | [Sapphire](https://www.tamtam.ai/c/sapphire) (sapphire.net)
Delivers comprehensive cyber solutions, integrating with client teams to protect digital infrastructure, mitigate risks, and maintain compliance through threat monitoring and strategic guidance. | Computer and Network Security | π¬π§ Newcastle upon Tyne | 477 | 1996 |
| 58 | [Intercity](https://www.tamtam.ai/c/intercity) (intercity.technology)
Intercity helps businesses improve their IT capabilities and solve technology issues, focusing on cloud, security, communications, and managed IT services | IT Services and IT Consulting | π¬π§ Birmingham | 472 | 1985 |
| 59 | [FSP](https://www.tamtam.ai/c/fsp) (fsp.co)
A leading digital transformation specialist, helping organizations with strategy, change, digital solutions, cloud, cybersecurity, data, and AI, recognized for exceptional workplace culture | IT Services and IT Consulting | π¬π§ Reading | 456 | 2012 |
| 60 | [Yoti](https://www.tamtam.ai/c/yoti) (yoti.com)
privacy-focused identity verification and age verification solutions helping businesses and individuals build trust while reducing fraud and enhancing data control | Software Development | π¬π§ London | 454 | 2014 |
| 61 | [Micro Focus (formerly HP / Hewlett Packard Enterprise)](https://www.tamtam.ai/c/micro-focus-formerly-hp-hewlett-packard-enterprise) (opentext.com)
A pure-play software company focused on maximizing ROI on existing software investments and enabling innovation in hybrid enterprise IT environments | Software Development | π¬π§ Newbury | 443 | 1976 |
| 62 | [Trustmarque](https://www.tamtam.ai/c/trustmarque) (trustmarque.com)
Delivers technology value through IT solutions, helping organizations acquire and adopt the right technology to create innovation across various IT domains. | IT Services and IT Consulting | π¬π§ York | 431 | 1987 |
| 63 | [Iomart](https://www.tamtam.ai/c/iomart) (iomart.com)
Cloud computing and IT managed services provider offering secure hybrid cloud, network connectivity, data management, and digital workplace capabilities to enable businesses to operate seamlessly | IT Services and IT Consulting | π¬π§ Glasgow | 426 | |
| 64 | [GL Noble Denton](https://www.tamtam.ai/c/gl-noble-denton) (dnvgl.com)
Global provider of risk management services dedicated to safeguarding life, property, and the environment, with a focus on safety, innovation, and sustainability | Oil and Gas | π¬π§ London | 423 | |
| 65 | [Air IT Group](https://www.tamtam.ai/c/air-it-group) (airit.co.uk)
Provides managed IT services including cybersecurity, business intelligence, automation, cloud solutions, and IT support to optimize and scale SME operations. | IT Services and IT Consulting | π¬π§ Nottingham | 419 | 2005 |
| 66 | [Hammer Distribution](https://www.tamtam.ai/c/hammer-distribution) (hammerdistribution.com)
An award-winning value-add distributor specializing in enterprise data storage, server, and networking solutions with a strong focus on customer service | Computer Hardware Manufacturing | π¬π§ Basingstoke | 419 | 1991 |
| 67 | [CREST](https://www.tamtam.ai/c/crest) (crest-approved.org)
An international organization ensuring quality in the global cyber security industry through accreditation, certification, and collaboration with various stakeholders worldwide | Computer and Network Security | π¬π§ London | 419 | |
| 68 | [Capula](https://www.tamtam.ai/c/capula) (capula.com)
A leader in system integration for industrial environments, focusing on digital transformation and operational technology to optimize efficiency, performance, and safety | Engineering Services | π¬π§ Stone | 412 | 1969 |
| 69 | [BCN](https://www.tamtam.ai/c/bcn-manchester) (bcn.co.uk)
Providing managed IT services, digital transformation guidance, cloud solutions, and security expertise to help organizations innovate and compete effectively. | IT Services and IT Consulting | π¬π§ Manchester | 412 | 2009 |
| 70 | [Elevate](https://www.tamtam.ai/c/elevate-manchester) (elevate.uk)
Providing affordable, hyperfast internet access to empower individuals, drive economic growth, and foster technological innovation worldwide. | Technology, Information and Internet | π¬π§ Manchester | 402 | 2014 |
| 71 | [PURVIEW](https://www.tamtam.ai/c/purview) (purviewservices.com)
Providing IT engineering and talent solutions to mid-market and Fortune 500 companies globally, with expertise in data, AI, cloud, and cybersecurity services. | IT Services and IT Consulting | π¬π§ Edinburgh | 395 | 2010 |
| 72 | [MBA](https://www.tamtam.ai/c/mba) (mba-it.com)
IT solutions and services provider in London, specializing in complex applications, enterprise capabilities, and exceptional service for businesses in finance, legal, and insurance sectors | IT Services and IT Consulting | π¬π§ London | 388 | 2005 |
| 73 | [Police Digital Service](https://www.tamtam.ai/c/police-digital-service) (pds.police.uk)
The company coordinates and delivers digital services for UK policing to use technology for public safety, working with various organizations | IT Services and IT Consulting | π¬π§ London | 379 | 2015 |
| 74 | [Bridewell](https://www.tamtam.ai/c/bridewell) (bridewell.com)
Trusted partner for cyber security, offering consulting and managed services, especially for Critical National Infrastructure, leveraging Microsoft Security technology for robust protection. | Computer and Network Security | π¬π§ Reading | 379 | 2013 |
| 75 | [S-RM](https://www.tamtam.ai/c/s-rm) (s-rminform.com)
It is a global intelligence and cyber security consultancy, providing critical decision-making support, resilience building, and crisis response for clients. | Security and Investigations | π¬π§ London | 373 | 2005 |
| 76 | [Pen AI](https://www.tamtam.ai/c/pen-ai) (gudens.com)
AI-powered writing tool with features like idea generation, content expansion, research assistance, overcoming writer's block, style control, grammar checking, and plagiarism detection Join the writing community | Computer and Network Security | π¬π§ London | 363 | |
| 77 | [Security Blue Team](https://www.tamtam.ai/c/security-blue-team) (centri.org)
It provides practical defensive cybersecurity training, free courses, certifications, and platforms like Blue Team Labs Online and CySec Careers. | Computer and Network Security | π¬π§ London | 354 | 2019 |
| 78 | [WorkNest People](https://www.tamtam.ai/c/worknest-people) (worknest.com)
WorkNest provides Employment Law, HR, and Health & Safety support services with technology platforms, proactive advice, and a team of experts to help employers overcome challenges | Legal Services | π¬π§ Aldford | 353 | |
| 79 | [PortSwigger](https://www.tamtam.ai/c/portswigger) (portswigger.net)
Develops software for web application security testing. The Burp Suite toolkit is a standard for web security professionals. Recruiting Java and .NET developers. | Software Development | π¬π§ Knutsford | 342 | 2008 |
| 80 | [Immersive](https://www.tamtam.ai/c/immersive) (immersivelabs.com)
Focuses on people-centric cyber resilience, aiming for organizations to be threat-ready and capable of demonstrating this readiness to leadership and stakeholders. | Computer and Network Security | π¬π§ Bristol | 335 | 2017 |
| 81 | [Kocho](https://www.tamtam.ai/c/kocho) (kocho.co.uk)
Empowering ambitious companies with Microsoft cloud solutions, identity, mobility, connectivity, and cyber security services for secure growth and business success | IT Services and IT Consulting | π¬π§ London | 332 | 2001 |
| 82 | [The Citation Group](https://www.tamtam.ai/c/the-citation-group) (thecitationgroup.com)
This company offers compliance and quality services with a focus on HR, Employment Law, Health and Safety, ISO Certification, and more globally | Legal Services | π¬π§ Wilmslow | 331 | 1995 |
| 83 | [Obrela](https://www.tamtam.ai/c/obrela) (obrela.com)
Provides real-time cyber risk management combining threat detection, response, and managed risk services to protect businesses worldwide. | IT Services and IT Consulting | π¬π§ London | 327 | 2010 |
| 84 | [Reliance Infosystems](https://www.tamtam.ai/c/reliance-infosystems) (reliance.systems)
Provides technology inputs to support business goals, creating partnerships to leverage technology for value propositions and competitive positioning in various industries. | IT Services and IT Consulting | π¬π§ West End | 321 | 2002 |
| 85 | [Aspire Technology Solutions](https://www.tamtam.ai/c/aspire-technology-solutions) (aspirets.com)
It is a leading UK provider of managed IT, cyber security, and workplace solutions, serving over 2,000 customers effectively. | IT Services and IT Consulting | π¬π§ Gateshead | 321 | 2006 |
| 86 | [Nomad Digital](https://www.tamtam.ai/c/nomad-digital) (nomad-digital.com)
A global leader in providing passenger and fleet management solutions for the transport industry, enhancing passenger experience and improving operational efficiency | Telecommunications | π¬π§ Newcastle upon Tyne | 321 | 2002 |
| 87 | [G3](https://www.tamtam.ai/c/g3-london) (g3.co)
Global advisory services providing intelligence for informed decisions on deals and markets, investigations for fraud and legal support, plus cyber threat defense. | Business Consulting and Services | π¬π§ London | 320 | 2004 |
| 88 | [Onfido](https://www.tamtam.ai/c/onfido) (entrust.com)
This company simplifies digital identity verification through a platform that combines document, biometric, and data verifications with AI-powered analysis | IT Services and IT Consulting | π¬π§ London | 318 | 2012 |
| 89 | [KYOCERA Document Solutions UK](https://www.tamtam.ai/c/kyocera-document-solutions-uk) (kyoceradocumentsolutions.co.uk)
Provider of eco-friendly multifunction printers, business applications, and consultative services to optimize and manage document workflows efficiently. | IT Services and IT Consulting | π¬π§ Reading | 318 | 1983 |
| 90 | [Six Degrees](https://www.tamtam.ai/c/six-degrees) (6dg.co.uk)
Providing AI-enabled, people-led technology services in Core, Hybrid Cloud, Cyber Security, and Modern Work aligned with client outcomes. | IT Services and IT Consulting | π¬π§ London | 313 | 2011 |
| 91 | [eCOGRA](https://www.tamtam.ai/c/ecogra) (ecogra.org)
An internationally accredited testing agency specializing in certifying online gambling software and systems, with expertise in information security management systems audits | Gambling Facilities and Casinos | π¬π§ London | 313 | 2003 |
| 92 | [Kape Technologies](https://www.tamtam.ai/c/kape-technologies) (kape.com)
It is a cybersecurity company dedicated to enhancing digital experiences through privacy and protection, with a global team of experts. | Software Development | π¬π§ London | 310 | |
| 93 | [ITI Group](https://www.tamtam.ai/c/iti-group) (itigroup.com)
ITI Group specializes in developing and integrating digital transformation solutions for the Energy, Nuclear, and Industrial manufacturing sectors, prioritizing safety, security, and sustainability | Software Development | π¬π§ Sheffield | 300 | 1972 |
| 94 | [Quorum Cyber](https://www.tamtam.ai/c/quorum-cyber) (quorumcyber.com)
Provides comprehensive cybersecurity solutions, including managed detection and response, incident response, and security consulting, helping organizations defend against cyber threats globally. | Computer and Network Security | π¬π§ Edinburgh | 292 | 2016 |
| 95 | [Netcraft](https://www.tamtam.ai/c/netcraft) (netcraft.com)
It offers phishing detection, cybercrime disruption, and website takedown solutions to major organizations, enhancing their online security and safety. | Technology, Information and Internet | π¬π§ London | 286 | 1994 |
| 96 | [A&O IT Group](https://www.tamtam.ai/c/a-and-o-it-group) (aoitgroup.com)
Provides global managed IT services, including field services, project management, warehousing, 24/7 support, network solutions, and cybersecurity consulting for various industries. | IT Services and IT Consulting | π¬π§ Bracknell | 283 | |
| 97 | [Vorboss](https://www.tamtam.ai/c/vorboss) (vorboss.com)
A dedicated fiber network provider in London offering 10Gbps minimum internet service for data-hungry businesses, recognized as a top workplace | Telecommunications | π¬π§ London | 280 | 2006 |
| 98 | [Featurespace](https://www.tamtam.ai/c/featurespace) (featurespace.com)
Global leader in Enterprise Financial Crime prevention with real-time machine learning software to prevent fraud and Anti-Money Laundering for financial institutions worldwide | Software Development | π¬π§ Cambridge | 279 | 2008 |
| 99 | [SBL](https://www.tamtam.ai/c/sbl) (boxxe.com)
A leading IT reseller established in 1987, specializing in Information Security solutions with a comprehensive portfolio of software, hardware, services, and training | IT Services and IT Consulting | π¬π§ York | 277 | 1987 |
| 100 | [Callsign](https://www.tamtam.ai/c/callsign) (callsign.com)
pioneers digital trust using proprietary technology that mimics human identification, providing privacy, safety, and minimal friction while blocking bad actors through highly accurate AI recognition. | Computer and Network Security | π¬π§ London | 276 | 2011 |
## How this list is built
Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 12, 2026.
## More company lists in the United Kingdom
- [The largest companies in the United Kingdom](https://www.tamtam.ai/l/largest-companies-united-kingdom) (36,548)
- [Multinational companies in the United Kingdom](https://www.tamtam.ai/l/multinational-companies-united-kingdom) (7,458)
- [Financial services firms in the United Kingdom](https://www.tamtam.ai/l/financial-services-firms-united-kingdom) (3,711)
- [Financial Services companies in the United Kingdom](https://www.tamtam.ai/l/financial-services-companies-united-kingdom) (3,696)
- [Retail chains in the United Kingdom](https://www.tamtam.ai/l/retail-chains-united-kingdom) (3,289)
- [Professional services firms in the United Kingdom](https://www.tamtam.ai/l/professional-services-firms-united-kingdom) (2,706)
- [Software Development companies in the United Kingdom](https://www.tamtam.ai/l/software-development-companies-united-kingdom) (2,600)
- [Manufacturers in the United Kingdom](https://www.tamtam.ai/l/manufacturers-united-kingdom) (2,159)
- [Companies with in-house R&D in the United Kingdom](https://www.tamtam.ai/l/r-and-d-companies-united-kingdom) (1,930)
- [IT Services and IT Consulting companies in the United Kingdom](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-united-kingdom) (1,722)
- [Retail companies in the United Kingdom](https://www.tamtam.ai/l/retail-companies-united-kingdom) (1,596)
- [IT services companies in the United Kingdom](https://www.tamtam.ai/l/it-services-companies-united-kingdom) (1,583)
- [Hotel and hospitality groups in the United Kingdom](https://www.tamtam.ai/l/hospitality-groups-united-kingdom) (1,461)
- [Companies with a mobile app in the United Kingdom](https://www.tamtam.ai/l/companies-with-mobile-app-united-kingdom) (1,411)
- [Consulting firms in the United Kingdom](https://www.tamtam.ai/l/consulting-firms-united-kingdom) (1,298)
- [E-commerce companies in the United Kingdom](https://www.tamtam.ai/l/ecommerce-companies-united-kingdom) (1,246)
- [Hardware manufacturers in the United Kingdom](https://www.tamtam.ai/l/hardware-companies-united-kingdom) (1,239)
- [Family-owned companies in the United Kingdom](https://www.tamtam.ai/l/family-owned-companies-united-kingdom) (1,224)
- [Hospitality companies in the United Kingdom](https://www.tamtam.ai/l/hospitality-companies-united-kingdom) (1,204)
- [Critical infrastructure operators in the United Kingdom](https://www.tamtam.ai/l/critical-infrastructure-operators-united-kingdom) (1,195)
- [Wellness and Fitness Services companies in the United Kingdom](https://www.tamtam.ai/l/wellness-and-fitness-services-companies-united-kingdom) (1,151)
- [Retail Apparel and Fashion companies in the United Kingdom](https://www.tamtam.ai/l/retail-apparel-and-fashion-companies-united-kingdom) (1,085)
- [Subscription businesses in the United Kingdom](https://www.tamtam.ai/l/subscription-businesses-united-kingdom) (1,077)
- [Distributors and wholesalers in the United Kingdom](https://www.tamtam.ai/l/distributors-and-wholesalers-united-kingdom) (1,060)
## The same list elsewhere in United Kingdom
- [Cybersecurity companies in London](https://www.tamtam.ai/l/cybersecurity-companies-london) (209)
## The same list elsewhere
- [Cybersecurity companies in the world](https://www.tamtam.ai/l/cybersecurity-companies-in-the-world) (3,776)
- [Cybersecurity companies in Europe](https://www.tamtam.ai/l/cybersecurity-companies-in-europe) (2,197)
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Source: https://www.tamtam.ai/l/cybersecurity-companies-united-kingdom