Company lists · Data refreshed September 2026

Top 24 Managed security companies based in London, United Kingdom

Name: Managed security companies based in London, United Kingdom
Creator: RevenueBase
License: https://creativecommons.org/licenses/by/4.0/

Compiled by the RevenueBase Data Team Data refreshed Sep 21, 2026 505 companies tracked

RevenueBase identified 505 managed security companies headquartered in London, United Kingdom as of September 2026 and tracks 87,912 professional contacts across them, including 1,799 with verified work emails. London is the largest hub.

This list covers managed security companies headquartered in London, United Kingdom, matched on what each company actually does as described in its own words. Ranked by team size, largest first. Every row shows the company's own description, its RevenueBase Smart Search rating, and when it was last checked. Data refreshed September 21, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase Smart Search, the natural-language company search RevenueBase customers use to build their own targeted lists and unlock verified emails and direct dials at the companies on them. How these lists are built and judged.

How to read this list HQ checked on every row RevenueBase Smart Search rating on every row Refreshed Sep 21, 2026 86% judged on-target in blind review

505Companies

87,912Contacts tracked

1,799Verified emails

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The 24 largest managed security companies based in London, United Kingdom

Ranked by team size

Top 24 of 505 managed security companies based in London, United Kingdom, ranked by team size, largest first. Data refreshed Sep 21, 2026. RevenueBase Smart Search rates how each company's information relates to managed security companies: strong evidence (its own description names it), partial (names part of it), indirect (matched on the rest of its profile rather than the description shown). Click a contact count to view that company's people.
#	Company	RevenueBase Smart Search	Headquarters	Employees	Contacts
1	G4s	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	10001+	79,699 contacts →
	Partial evidence “G4S is a leading security and facility services company that provides proactive security services and cutting-edge smart technology to deliver tailored, integrated security…” Source: RevenueBase Database · checked Sep 21, 2026
2	CIS Security Limited	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	919 contacts →
	Partial evidence “CIS Security is an independent security company equipped to help customers to solve the complex challenges in today’s digital, connected and regulated business world.” Source: RevenueBase Database · checked Sep 21, 2026
3	Corps Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	847 contacts →
	Partial evidence “Corps Security - experts in security with social value Built on over 165 years of experience, Corps provides specialist security services, across the UK, to ensure the safety of…” Source: RevenueBase Database · checked Sep 21, 2026
4	Ward Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	419 contacts →
	Partial evidence “Ward is an award winning, privately owned business, providing bespoke risk and security solutions including protective security personnel, explosive search dogs, narcotic search…” Source: RevenueBase Database · checked Sep 21, 2026
5	Obrela	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	242 contacts →
	Partial evidence “Obrela Security Industries is a global provider of cyber security services.” Source: RevenueBase Database · checked Sep 21, 2026
6	Intragen	Strong evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	190 contacts →
	Strong evidence “Intragen is a cyber security business focused on managed Identity solutions and services.” Source: RevenueBase Database · checked Sep 21, 2026
7	The Keyholding Company	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	137 contacts →
	Partial evidence “The Keyholding Company are a tech-enabled mobile security services company, specialising in alarm response, mobile patrols, locks and unlocks, emergency and temporary guarding…” Source: RevenueBase Database · checked Sep 21, 2026
8	Vigilant Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	133 contacts →
	Partial evidence “Vigilant Security provides a range of services including keyholding, corporate security, event security, mobile patrols as well as specialist services throughout the UK.” Source: RevenueBase Database · checked Sep 21, 2026
9	City Group Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	124 contacts →
	Partial evidence “CGS is a dynamic and professional FM company, specialising in customer focussed security provisions and cleaning specialists.” Source: RevenueBase Database · checked Sep 21, 2026
10	Bulletproof Cyber Security	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	123 contacts →
	Indirect evidence “Bulletproof is now part of WorkNest Secure.” Source: RevenueBase Database · checked Sep 21, 2026
11	Conosco	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	105 contacts →
	Indirect evidence “Cybersecurity specialists providing technology and telecoms solutions that gives you the leadership, experience and resilience you need to build and secure the future of work.” Source: RevenueBase Database · checked Sep 21, 2026
12	Cyberone	Strong evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	96 contacts →
	Strong evidence “CyberOne is a Microsoft Security Elite Partner and one of only 100 global Microsoft partners recognised with Microsoft-Verified Managed XDR solution status.” Source: RevenueBase Database · checked Sep 21, 2026
13	ITC Secure	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	87 contacts →
	Partial evidence “ITC Secure is an advisory-led cyber security services company.” Source: RevenueBase Database · checked Sep 21, 2026
14	Cybersmart	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	84 contacts →
	Indirect evidence “Cybersecurity should be simple.” Source: RevenueBase Database · checked Sep 21, 2026
15	Cybanetix	Strong evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	79 contacts →
	Strong evidence “Cybanetix is a leading provider of managed Cyber Security Service and hosted SIEM and breach detection services.” Source: RevenueBase Database · checked Sep 21, 2026
16	Lead Element Security Group	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	75 contacts →
	Partial evidence “We are Veteran Owned, Veteran Operated Security company based in London (HQ), with operation nationwide.” Source: RevenueBase Database · checked Sep 21, 2026
17	City Security Services Part Of City Group Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	64 contacts →
	Partial evidence “City Security Services (CSS) have more than 25 years’ experience within the corporate security, public sector, education and social housing markets delivering manned guarding…” Source: RevenueBase Database · checked Sep 21, 2026
18	Vigilance Certified B Corp	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	63 contacts →
	Partial evidence “Vigilance is a pioneering security company with a proud military heritage.” Source: RevenueBase Database · checked Sep 21, 2026
19	Threatspike	Strong evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	61 contacts →
	Strong evidence “ThreatSpike is the world's first AI-managed IT and security platform, replacing the legacy MSP model entirely.” Source: RevenueBase Database · checked Sep 21, 2026
20	Techforing	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	61 contacts →
	Indirect evidence “TechForing is a global leader in cybersecurity, dedicated to protecting digital assets and ensuring a safer cyberspace for businesses and individuals.” Source: RevenueBase Database · checked Sep 21, 2026
21	Hexegic	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	52 contacts →
	Indirect evidence “At Hexegic we are not just passionate about protecting data through our Cyber services we are passionate about helping companies release the potential of the data they hold…” Source: RevenueBase Database · checked Sep 21, 2026
22	Redscan, A Kroll Business	Strong evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	51 contacts →
	Strong evidence “Redscan is an award-winning provider of managed security services, specialising in Managed Detection and Response, Penetration Testing and Red Teaming.” Source: RevenueBase Database · checked Sep 21, 2026
23	UK Protection LTD	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	45 contacts →
	Partial evidence “UK Protection is widely recognised as the premier supplier of security solutions to the Corporate, Jewellery and Luxury Retail industries across the UK.” Source: RevenueBase Database · checked Sep 21, 2026
24	Ak9 Security And FM Solutions LTD	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	501-1,000	43 contacts →
	Partial evidence “AK9 Security and FM Solutions offers comprehensive security solutions for businesses, governmental organizations, and residential areas.” Source: RevenueBase Database · checked Sep 21, 2026

RevenueBase Smart Search

RevenueBase Smart Search assesses information from a company’s LinkedIn profile, information supplied directly by the company, its website, and other publicly available sources. It uses that information to rate how closely the company relates to this list’s category: managed security companies. Every row carries its rating and the description the rating was read from, so each one can be checked rather than taken on trust.

Strong evidence: The company's own public description of its business names managed security companies.
Partial evidence: Its own public description names part of managed security companies, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name managed security companies. The match rests on the rest of the company's public profile rather than the one sentence quoted here, so this is the rating to check first.

RevenueBase Smart Search is how these lists are built: RevenueBase's data engine and AI assemble the companies that match a category defined in a user's own words, so a list can be about what companies actually do rather than about whichever industry code they were filed under.

Showing 24 of 505 managed security companies based in London, United Kingdom

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Managed security companies based in London, United Kingdom at a glance

As of Sep 21, 2026

2.0%Verified-email coverage

174.1Average contacts per company

11-50Median size (employees)

100.0%Largest-city concentration · London

Sep 21, 2026Page data refreshed

Companies by employee count

1-10

197

11-50

164

51-200

201-500

501-1,000

1,001-5,000

10001+

Email recency for this list is measured across the whole United Kingdom list rather than for London, so it is reported there. Company counts and contact totals on this page are exact for London, over 505 companies.

How this list was built

Company categories are rarely black and white. RevenueBase reads each company's own description of its business to decide whether it belongs among managed security companies, so some rows will be adjacent to the category rather than pure plays. The description and RevenueBase Smart Search rating on every row are there so you can check each match yourself.

Source: The RevenueBase company graph: 60 million companies and 398.9 million professional contacts resolved from primary sources, queried with RevenueBase Smart Search, the natural-language company search available to every RevenueBase user.
What qualifies: Companies headquartered in London, United Kingdom whose own description of what they do matches “managed security companies”. Matching reads each company's description, not its industry code or its name.
RevenueBase Smart Search: RevenueBase Smart Search is how this list is assembled and how each row is rated. RevenueBase's data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to a category defined in a user's own words. Each row is rated strong evidence (its own description names managed security companies), partial evidence (it names part of the category) or indirect evidence (the description shown names none of it and the match rests on the rest of the company's profile). The description supporting each rating is quoted on the row.
What we exclude: Companies whose own description does not clearly place them among managed security companies, and records with no verified work email. Companies headquartered outside London are excluded even when they keep an office there.
Match quality: In blind human judging of this matching method, 86% of matched companies were on target. Expect roughly 1 in 7 rows to be adjacent to the category rather than a pure play. Every row shows the company's own description and its RevenueBase Smart Search rating so you can judge each match yourself. Read the full methodology: how the lists are built, how the judging worked, and what the figure means.
Ranking: Team size, largest first: companies are ordered by the number of professionals RevenueBase tracks at each one. Employee ranges shown are reported bands, for context.
Verification: Every listed company carries at least one verified work email, 1,799 across the full list. Contacts re-verify on a rolling cadence, and each contact's own verification date is shown inside RevenueBase.
Refresh: This page's figures were pulled from the company graph on September 21, 2026. Lists refresh periodically as the graph is re-checked.
Corrections: Wrong category, wrong headquarters, or a company that has closed? Use “Report an issue” on any row. Reports go to the RevenueBase Data Team and feed back into the company graph.

Managed security companies by metro in the United Kingdom

Managed security companies in London505
Managed security companies in Manchester59
Managed security companies in Birmingham46
Managed security companies in Leeds25

Frequently asked

What is RevenueBase Smart Search?

RevenueBase Smart Search is how RevenueBase decides which companies belong on this list and how strongly each one fits. Its data engine and AI assess a company's LinkedIn profile, information supplied directly by the company, its website and other publicly available information, then relate it to the category the list is about. Each row is rated strong evidence when the company's own description names managed security companies, partial evidence when it names part of the category, and indirect evidence when the description shown names none of it and the match rests on the rest of the company's profile.

How many managed security companies are there based in London, United Kingdom?

RevenueBase identified 505 managed security companies headquartered in London, United Kingdom as of September 2026, matched on each company's own description of what it does rather than its industry code.

What is the largest company on this list?

G4s, headquartered in London, tops this list with the largest team on record.

Which city has the most managed security companies?

London leads with 505 headquartered companies, followed by Manchester (59) and Birmingham (46).

How do I get contact information for these companies?

A free RevenueBase account lets you run this exact search and work the top results, verified emails and direct dials included. Upgrading unlocks all 1,799 verified decision-maker contacts tracked across these 505 companies.

How current is this list?

The list refreshes periodically as the company graph is re-checked. This page's figures were pulled on September 21, 2026.

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About this data

RevenueBase is a B2B data infrastructure company. Its company graph covers 60 million companies and 398.9 million professional contacts, with emails verified on a rolling cadence rather than scraped once and left to decay. These company lists are generated directly from that graph with RevenueBase Smart Search, the same natural-language company search every RevenueBase user has: describe a market in plain words, get the companies that match, and add verified emails and direct dials for the people at them. It is the same data that powers RevenueBase's B2B data products, and a free account includes 500 credits to start. How these lists are built and judged.