Company lists · Data refreshed September 2026

Top 23 Security and access control companies based in London, United Kingdom

Name: Security and access control 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 6, 2026 346 companies tracked

RevenueBase identified 346 security and access control companies headquartered in London, United Kingdom as of September 2026 and tracks 82,346 professional contacts across them, including 867 with verified work emails. London is the largest hub.

This list covers security and access control 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, how directly it supports the match, and when it was last checked. Data refreshed September 6, 2026.

Published by RevenueBase, a B2B data infrastructure company. This list was built with RevenueBase SmartSearch, 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 Match evidence on every row Refreshed Sep 6, 2026 86% judged on-target in blind review

346Companies

82,346Contacts tracked

867Verified emails

Explore all 346 companies → Free signup · no credit card · 500 free credits

The 23 largest security and access control companies based in London, United Kingdom

Ranked by team size

Top 23 of 346 security and access control companies based in London, United Kingdom, ranked by team size, largest first. Data refreshed Sep 6, 2026. Evidence rates how directly each company's own description names security and access control companies: strong (names it), partial (names part of it), indirect (matched on its full profile rather than the summary shown). Click a count to unlock that company's people.
#	Company	Headquarters	Employees	Contacts
1	G4sPartial evidence	London, United KingdomHQ checked Sep 6, 2026	10001+	79,699
	“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: company website · checked Sep 6, 2026
2	QCICPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	159
	“QCIC is an award-winning global engineering firm specialising in designing, building and running security systems.” Source: company website · checked Sep 6, 2026
3	The Keyholding CompanyPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	137
	“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: company website · checked Sep 6, 2026
4	City Security Services Part Of City Group SecurityPartial evidence	London, United KingdomHQ checked Sep 6, 2026	201-500	64
	“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: company website · checked Sep 6, 2026
5	WLSPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	61
	“WLS (West London Security) has been providing security and solutions to London's homes and businesses for over 40 years.” Source: company website · checked Sep 6, 2026
6	Black Diamond SecurityPartial evidence	London, United KingdomHQ checked Sep 6, 2026	201-500	58
	“Black Diamond Security - Safeguarding Your World.” Source: company website · checked Sep 6, 2026
7	Custom Intelligent SecurityPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	51
	“Established in Custom Intelligent Security is a technology driven ISO27001 & NSi Gold Accredited independent electronic security specialist with a proven track record of…” Source: company website · checked Sep 6, 2026
8	Sensetech Systems LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	50
	“Sensetech Systems Ltd is an LPS1014 Accredited independent Fire Alarm, Security and Structured Data Cabling Company.” Source: company website · checked Sep 6, 2026
9	Electranet UK LimitedIndirect evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	49
	“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: company website · checked Sep 6, 2026
10	Ak9 Security And FM Solutions LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	501-1,000	43
	“AK9 Security and FM Solutions offers comprehensive security solutions for businesses, governmental organizations, and residential areas.” Source: company website · checked Sep 6, 2026
11	SMC Smart HomesIndirect evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	41
	“SMC are a leading custom electronic system design, installation and aftercare company.” Source: company website · checked Sep 6, 2026
12	Gratte Brothers Security Systems & SoftwarePartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	39
	“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: company website · checked Sep 6, 2026
13	Universal Security Systems LTDStrong evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	39
	“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: company website · checked Sep 6, 2026
14	BML GroupPartial evidence	London, United KingdomHQ checked Sep 6, 2026	11-50	37
	“Founded in 2015, BML Group is one of the UK's leading Security & Facilities Management providers, delivering tailored solutions that enhance operational efficiency and safety.” Source: company website · checked Sep 6, 2026
15	VidexukStrong evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	36
	“We are the experts in door entry and access control and have been supplying and manufacturing systems for 40 years.” Source: company website · checked Sep 6, 2026
16	ECS Systems LTDIndirect evidence	London, United KingdomHQ checked Sep 6, 2026	11-50	35
	“Here at ECS Systems we pride ourselves on providing the highest level of personalised service, to every client.” Source: company website · checked Sep 6, 2026
17	Pafi LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	32
	“Pafi Ltd, Was formed in 1995 to design, install and maintain integrated security solutions for the commercial market.” Source: company website · checked Sep 6, 2026
18	Systematic Security LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	201-500	31
	“Systematic Security deliver static manned guarding, mobile patrols, open and lock ups, keyholding and emergency response requirements as well as Vacant Property inspections to a…” Source: company website · checked Sep 6, 2026
19	DS Security Group LTDStrong evidence	London, United KingdomHQ checked Sep 6, 2026	11-50	27
	“CCTV and Access Control Service and installation specialists Established in 1993 DS Security prides itself on customer service.” Source: company website · checked Sep 6, 2026
20	Welcome GateStrong evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	23
	“Who are you… Most likely you are a Workplace or IT Professional with a lot on your plate including physical electronic security systems, such as - Access control - CCTV - Intruder…” Source: company website · checked Sep 6, 2026
21	Dennis Johns Service GroupStrong evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	20
	“The Dennis Johns Service Group is a forward thinking group of companies providing, Electrical, CCTV and Access Control, installation and maintenance contracting services.” Source: company website · checked Sep 6, 2026
22	Line Security Services LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	51-200	17
	“As a security services provider, protecting people and assets is our top priority.” Source: company website · checked Sep 6, 2026
23	SSG Support Services Group LTDPartial evidence	London, United KingdomHQ checked Sep 6, 2026	201-500	16
	“SSG Support Services Group LTD is specialists in provision of Manned guarding Security Services, Door Supervision, Security Guarding, Out of Hours Support, Concierge, Front of…” Source: company website · checked Sep 6, 2026

Showing 23 of 346 security and access control companies based in London, United Kingdom

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Security and access control companies based in London, United Kingdom at a glance

As of Sep 6, 2026

1-10Median size (employees)

LondonLargest hub · 346 HQs

Contacts with mobile numbers

Sep 6, 2026Data refreshed

Companies by employee count

1-10

172

11-50

105

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 this city, so it is reported there. Company counts and contact totals on this page are exact for London, over 346 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 and access control companies, so some rows will be adjacent to the category rather than pure plays. The description and evidence 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 SmartSearch, 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 and access control companies”. Matching reads each company's description, not its industry code or its name.
What we exclude: Companies whose own description does not clearly place them among security and access control 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 an evidence 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, 867 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 6, 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 and access control companies by metro in the United Kingdom

Security and access control companies in London346
Security and access control companies in Manchester73
Security and access control companies in Birmingham49
Security and access control companies in Glasgow36
Security and access control companies in Leeds31
Security and access control companies in Nottingham30
Security and access control companies in Belfast28
Security and access control companies in Leicester27
Security and access control companies in Liverpool27
Security and access control companies in Bristol26
Security and access control companies in Sheffield25

Frequently asked

How many security and access control companies are there based in London, United Kingdom?

RevenueBase identified 346 security and access control 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 security and access control companies?

London leads with 346 headquartered companies, followed by Manchester (73) and Birmingham (49).

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 867 verified decision-maker contacts tracked across these 346 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 6, 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 SmartSearch, 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.