Company lists · Data refreshed September 2026

Top 25 Security integrators based in London, United Kingdom

Name: Security integrators 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 542 companies tracked

RevenueBase identified 542 security integrators headquartered in London, United Kingdom as of September 2026 and tracks 86,217 professional contacts across them, including 2,009 with verified work emails. London is the largest hub.

This list covers security integrators 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

542Companies

86,217Contacts tracked

2,009Verified emails

Explore this list → Free signup · no credit card · 500 free credits

The 25 largest security integrators based in London, United Kingdom

Ranked by team size

Top 25 of 542 security integrators 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 security integrators: 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	Argenbright Security Europe Limited - Asel	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	5,001-10,000	358 contacts →
	Partial evidence “ASEL design, develop and deliver fully bespoke and integrated security solutions, seamlessly bringing together people, technology and processes to achieve results-driven outcomes.” Source: RevenueBase Database · checked Sep 21, 2026
5	GBE Converge Part Of Mitie	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	501-1,000	169 contacts →
	Partial evidence “As a member of Mitie Group a leading facilities management and professional services company GBE Converge brings an unparalleled expertise in Fire, Security, and IT systems.” Source: RevenueBase Database · checked Sep 21, 2026
6	QCIC	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	159 contacts →
	Partial evidence “QCIC is an award-winning global engineering firm specialising in designing, building and running security systems.” Source: RevenueBase Database · checked Sep 21, 2026
7	LMG Lmgiq.com	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	153 contacts →
	Indirect evidence “For 40 years, LMG has delivered secure, resilient and proven digital infrastructure solutions across the built environment.” Source: RevenueBase Database · checked Sep 21, 2026
8	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
9	Infinigate UK & Ireland	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	1,001-5,000	115 contacts →
	Indirect evidence “The Infinigate Group is a value-added distributor, fully committed to sustainable, leading-edge cybersecurity solutions.” Source: RevenueBase Database · checked Sep 21, 2026
10	Caretower An Integrity360 Company	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	97 contacts →
	Partial evidence “As an independent IT security specialist, Caretower provide comprehensive solutions to individual problems, thus allowing our recommendations to be unbiased.” Source: RevenueBase Database · checked Sep 21, 2026
11	Crossover	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	11-50	82 contacts →
	Partial evidence “Crossover is a leading audiovisual systems integrator – we deliver AV that’s high quality, powerful, simple to use, and reliable.” Source: RevenueBase Database · checked Sep 21, 2026
12	Nephos Technologies	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	80 contacts →
	Partial evidence “Nephos Technologies is an independent data systems integrator, specialising in helping organisations transform the way they store, manage and protect their data.” Source: RevenueBase Database · checked Sep 21, 2026
13	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
14	WLS	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	61 contacts →
	Partial evidence “WLS (West London Security) has been providing security and solutions to London's homes and businesses for over 40 years.” Source: RevenueBase Database · checked Sep 21, 2026
15	Garrison NOW A Part Of Everfox	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	60 contacts →
	Indirect evidence “Garrison is a London-based cybersecurity company founded in 2014 by David Garfield (CEO) and Henry Harrison (Chief Scientist).” Source: RevenueBase Database · checked Sep 21, 2026
16	Black Diamond Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	201-500	58 contacts →
	Partial evidence “Black Diamond Security - Safeguarding Your World.” Source: RevenueBase Database · checked Sep 21, 2026
17	Custom Intelligent Security	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	51 contacts →
	Partial evidence “Established in Custom Intelligent Security is a technology driven ISO27001 & NSi Gold Accredited independent electronic security specialist with a proven track record of…” Source: RevenueBase Database · checked Sep 21, 2026
18	Sensetech Systems LTD	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	50 contacts →
	Partial evidence “Sensetech Systems Ltd is an LPS1014 Accredited independent Fire Alarm, Security and Structured Data Cabling Company.” Source: RevenueBase Database · checked Sep 21, 2026
19	Electranet UK Limited	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	49 contacts →
	Indirect evidence “Electranet’s mission is to be a preferred partner to the public and private sectors, bringing competitively priced, secure and innovative solutions to the market.” Source: RevenueBase Database · checked Sep 21, 2026
20	Cornerstone	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	44 contacts →
	Partial evidence “CornerStone is an award winning, independent, security and digital building consulting firm with headquarters in the UK.” Source: RevenueBase Database · checked Sep 21, 2026
21	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
22	SMC Smart Homes	Indirect evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	41 contacts →
	Indirect evidence “SMC are a leading custom electronic system design, installation and aftercare company.” Source: RevenueBase Database · checked Sep 21, 2026
23	Gratte Brothers Security Systems & Software	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	39 contacts →
	Partial evidence “Gratte Brothers is an experienced provider of integrated security solutions, which are Built on Strong Values and ultimately deliver a measurable return on investment.” Source: RevenueBase Database · checked Sep 21, 2026
24	Universal Security Systems LTD	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	39 contacts →
	Partial evidence “Universal Security Systems Limited is a specialist provider of installation and maintenance services for all types of security systems including Access Control, Closed Circuit…” Source: RevenueBase Database · checked Sep 21, 2026
25	Link Media Systems	Partial evidence	London, United KingdomHQ checked Sep 21, 2026	51-200	37 contacts →
	Partial evidence “We are systems integrators.” 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: security integrators. 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 security integrators.
Partial evidence: Its own public description names part of security integrators, so it works in or next to the category without describing itself that way.
Indirect evidence: The description shown does not name security integrators. 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 25 of 542 security integrators based in London, United Kingdom

See the full list, filter by size, metro and specialty, and get verified emails and direct dials for all 2,009 reachable decision-makers.

Free signup · no credit card

View the full list →

Security integrators based in London, United Kingdom at a glance

As of Sep 21, 2026

2.3%Verified-email coverage

159.1Average contacts per company

1-10Median size (employees)

100.0%Largest-city concentration · London

Sep 21, 2026Page data refreshed

Companies by employee count

1-10

281

11-50

166

51-200

201-500

501-1,000

1,001-5,000

5,001-10,000

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 542 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 security integrators, 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 “security integrators”. 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 security integrators), 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 security integrators, 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, 2,009 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.

Security integrators by metro in the United Kingdom

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 security integrators, 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 security integrators are there based in London, United Kingdom?

RevenueBase identified 542 security integrators 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 security integrators?

London leads with 542 headquartered companies, followed by Manchester (63) and Birmingham (53).

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 2,009 verified decision-maker contacts tracked across these 542 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.

Ready to reach these companies? Verified emails and direct dials for all 542 security integrators based in London, United Kingdom. Start with a free account, no credit card.

Download this list →

Related lists

Security integrators by geography

Browse the directory

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.