Choosing between security companies in London is more complicated than comparing star ratings or choosing the largest name.
London’s private-security market includes multinational contractors, corporate guarding specialists, aviation-security businesses, event-security companies, construction specialists, mobile patrol operators, remote-monitoring providers and companies focused almost entirely on keyholding and alarm response.
Those businesses should not be judged as though they all provide the same service.
For this 2026 update, Companies.london reviewed a research pool of 50 security providers serving London before selecting ten companies for the main comparison.
Our research considered current Security Industry Authority information, evidence of London operations, the range of approved security activities, specialist expertise, service transparency and whether there was a clear reason for a London customer to shortlist each business.
The result is not simply another list of ten companies.
It is a comparison designed to answer a more useful question:
Which London security company appears best suited to the particular risk you need to manage?
Research checked: October 2026
What We Found From Our London Security Research
Several findings stood out.
All ten companies in our final shortlist currently hold SIA Approved Contractor Scheme approval for Security Guarding.
Nine of the ten are approved for Key Holding and nine for Public Space Surveillance (CCTV).
Six are approved for Door Supervision.
Only one of our final ten currently includes Close Protection within its ACS activities, while one includes Vehicle Immobilisation.
Across the final ten companies, there are 36 individual ACS activity approvals, producing an average of 3.6 approved activities per shortlisted company.
Half of our Top 10 hold ACS approval across at least four different activities.
These figures are Companies.london calculations based on the current SIA entries of the ten companies selected for this guide.
They should not be interpreted as a statistical picture of every London security company.
They do, however, reveal something useful: most of the companies making our final list are not limited to conventional static guarding.
London Presence Is Not the Same as a London Registered Address
We also checked whether our finalists had credible London operations.
Seven of the ten use a London postal address on their current SIA contractor entry.
The remaining three still have independently verifiable London operations.
Securitas, for example, has dedicated London operations, while Ward Security operates from a City of London location alongside its wider UK network.
That means all ten finalists have a verifiable London presence, but it would be inaccurate to describe all ten simply as London-headquartered companies.
That distinction is important when comparing providers.
How Large Is the SIA Approved Contractor Market?
The SIA said in June 2026 that it approved 734 security businesses through its Approved Contractor Scheme.
It also reported that the 85 largest businesses by turnover accounted for around 40% of the UK private-security market and employed approximately 30% of individual SIA licence holders.
That suggests the industry combines a relatively small group of very large providers with hundreds of smaller and specialist contractors.
This is one reason company size alone was not used to determine our ranking.
The 50 Security Companies Included in Our Research
The research universe was intentionally wider than the final ranking.
It included large integrated contractors, London independents and specialists competing in individual areas of the security market.
This longlist is not intended to claim that the remaining 40 companies are poor providers.
Some were stronger in narrow areas than in an overall London comparison.
For example, an event-security specialist could be a better choice for a festival or stadium than several companies appearing in our overall Top 10.
How We Selected the Final 10?
We deliberately avoided creating a complicated 97/100-style score when several important security qualities cannot be measured objectively from public information.
A numerical score can look scientific while actually hiding subjective assumptions.
Instead, each finalist had to perform strongly across London operational evidence, current SIA ACS information, service breadth, specialist capability and public transparency.
London Operational Evidence
We looked for an office, operational location, London-specific infrastructure or other credible evidence that the company genuinely operates in the capital.
Current SIA ACS Information
We checked the activities appearing on the SIA’s Approved Contractor register rather than relying solely on accreditation badges displayed on company websites.
Service Breadth
Broader capability can be useful for organisations wanting guarding, keyholding, CCTV and response services from one supplier.
Breadth was not treated as automatically better.
Specialist Capability
A provider with genuine aviation, event, monitoring or keyholding expertise can outperform a larger generalist when a customer’s requirement is specialised.
Transparency and Evidence
We gave more weight to independently checkable information than claims such as “leading”, “trusted” or “best”.
Top 10 Security Companies in London Compared
SG: Security Guarding · DS: Door Supervision · KH: Key Holding · CP: Close Protection · CCTV: Public Space Surveillance · VI: Vehicle Immobilisation
This is an independent Companies.london editorial ranking and is not an SIA ranking.
1. Mitie
Best Overall for Large Integrated Security Requirements
Mitie takes our first position because few companies in the final comparison combine its breadth of ACS approval with its scale and London presence.
The current SIA register shows Mitie approved for Security Guarding, CCTV, Door Supervision, Key Holding and Close Protection, giving it five ACS activities.
A large organisation may simultaneously require officers, reception security, surveillance, alarm response, access control and protection around higher-risk personnel or events.
Using one integrated security operation can sometimes be easier than coordinating several unrelated suppliers.
Mitie’s wider role in workplace and building operations also makes it relevant to businesses comparing Facility Management Companies in London.
Companies.london verdict: Best starting point for major organisations seeking an integrated security provider rather than a single-purpose guarding company.
Official website: https://www.mitie.com/
2. CIS Security
Best for London Corporate Buildings and Premium Property
CIS Security ranks particularly strongly because its proposition is closely aligned with London’s corporate-property market.
Its current SIA approval includes Security Guarding, CCTV, Door Supervision and Key Holding.
CIS publicly identifies corporate buildings, estate management, education and public-sector sites, cultural venues, life sciences and critical environments among its sectors.
Corporate buildings present a different security problem from warehouses or vacant sites.
Officers may simultaneously manage visitors, identify suspicious behaviour, support emergency procedures, control access and represent the building professionally.
This is particularly relevant to businesses already working with Estate Management Companies in London.
Companies.london verdict: One of our strongest candidates for office buildings, managed commercial property and corporate headquarters in London.
Official website: https://cis-security.co.uk/
3. Corps Security
Best for Guarding Combined With Monitoring
Corps Security takes third place because monitoring is an important part of its wider security proposition rather than simply an optional add-on.
Its current ACS approval covers Security Guarding, Key Holding, CCTV and Door Supervision, and its registered office is at Cowcross Street in London.
Corps combines guarding with monitoring, consultancy and integrated-security services. The company also describes itself as a social enterprise and reports a history dating to 1859.
The significance is operational.
Not every part of a building necessarily requires permanent human observation. Remote surveillance, alarms and monitoring can allow physical officers to concentrate on entrances, incidents and areas where human intervention creates the greatest value.
Companies.london verdict: Particularly interesting for businesses seeking to combine officers with remote monitoring rather than simply purchasing more guard hours.
Official website: https://www.corpssecurity.co.uk/
4. G4S Secure Solutions
Best for Large and Operationally Complex Contracts
G4S remains one of the strongest options where scale and operational resilience are major considerations.
Its security operation includes guarding alongside security technology and wider integrated services. Its current UK website also highlights major infrastructure and event-security work.
Large security contracts often require more than filling a rota.
Management capability, relief personnel, escalation structures, training, monitoring and the ability to mobilise across multiple locations become increasingly important as a contract grows.
This is where the infrastructure of providers such as G4S can become an advantage.
Companies.london verdict: Strong option for enterprises, major estates and security requirements where mobilisation and scale matter as much as individual services.
Official website: https://www.g4s.com/
5. Bidvest Noonan
Best for Security Integrated With Facilities Management
Bidvest Noonan is another finalist with broad security capabilities and a strong facilities-management connection.
Its London office is at Old Broad Street, while the wider business combines security with integrated facilities services.
Its inclusion is particularly relevant where security forms part of a larger facilities contract.
In offices, shopping environments, healthcare property and large estates, guarding does not exist in isolation.
Security staff may interact with cleaning teams, facilities managers, reception staff, engineering contractors and building-management functions.
Businesses assessing that model should also compare our Facility Management Companies in London.
Companies.london verdict: Strong candidate where security is being purchased alongside wider building and facilities services.
Official website: https://bidvestnoonan.com/
6. Wilson James
Best for Aviation and Complex Operational Environments
Wilson James differs from several companies above it because specialist operational experience is a major reason for its inclusion.
The business works across aviation, transport, construction, cultural venues, defence, energy, healthcare, real estate, retail and other complex operating environments.
Its aviation capabilities cover environments where screening, controlled access, operational continuity and regulatory requirements can be fundamentally different from ordinary static guarding.
Wilson James is also relevant to major built-environment projects. Businesses researching that market can compare our separate guide to Construction Companies in London.
Companies.london verdict: One of the most interesting companies in our research for aviation, transport and other complex, high-throughput operating environments.
Official website: https://wilsonjames.co.uk/
7. ICTS UK
Best for Aviation and Highly Regulated Security
ICTS is another specialist that cannot be judged purely by the number of services it offers.
ICTS reports more than 4,800 personnel in the UK, operations across more than 144 UK locations and over 39 years of experience in highly regulated industries.
Its services span personnel, canine security and technology.
For an ordinary small office, a broader London guarding provider might be more appropriate.
For aviation and similarly regulated environments, specialist experience becomes much more important.
Companies.london verdict: Strong specialist choice where regulation and formal security procedures matter more than having the widest general-service catalogue.
Official website: https://www.icts.co.uk/
8. Securitas
Best for Combining Physical and Electronic Security
Securitas combines professional guarding with mobile, remote and electronic-security services.
Its UK operation offers remote surveillance, mobile guarding, on-site security, electronic security and corporate-risk services.
The company has operated in the UK since 1973 and forms part of a global business with decades of security experience.
This combination is increasingly relevant.
The decision is no longer always between “having guards” and “using technology”.
Many security strategies combine cameras, alarms, access systems and monitoring with officers who intervene where human judgement is required.
Businesses should, however, distinguish physical protection from IT and data protection. Companies primarily concerned about digital attacks should separately compare specialist Cyber Security Companies in London.
Companies.london verdict: Strong all-round option for organisations seeking both physical security personnel and electronic protection.
Official website: https://www.securitas.uk.com/uk/
9. Ward Security
Best for Commercial Property and Mobile Security
Ward Security currently holds ACS approval for Security Guarding, Key Holding and CCTV.
The company provides protective personnel alongside mobile services, alarm response, keyholding, property security and technology-based solutions.
Its London operation makes it particularly relevant to commercial-property owners and managers whose sites may require a mixture of permanent guards, mobile visits, monitoring and out-of-hours response.
A property portfolio does not necessarily require one guard standing at every location.
Risk, occupancy, alarms and operating hours should determine the security model.
Landlords and property operators can also compare Property Management Companies in London and Estate Management Companies in London when reviewing the wider management of their assets.
Companies.london verdict: Strong shortlist candidate for commercial buildings and multi-site property portfolios.
Official website: https://www.ward-security.co.uk/
10. The Keyholding Company
Best Specialist for Keyholding and Alarm Response
The Keyholding Company demonstrates why specialist providers should not automatically lose to large integrated contractors.
Its core model revolves around keyholding, alarm response, patrols, vacant-property checks and temporary guarding.
The company says its nationwide network covers 99.8% of UK postcodes, supported by a technology platform that matches response requirements with available officers.
Its operating model is different from traditional static guarding.
Keyholding commonly involves secure key custody combined with a response service when an alarm activates or access is required.
For a retailer or business managing many empty premises overnight, this can be fundamentally different from paying for permanent officers at every site.
Companies.london verdict: Our specialist selection where keyholding, alarm response and mobile attendance are more important than permanent guarding.
Official website: https://www.keyholding.com/
Which Security Company Is Best for Different Requirements?
The overall ranking should not be treated as a universal answer.
Which Companies Stood Out Outside the Top 10?
Some companies in the wider 50-company review deserve attention because their strongest capabilities are specialist rather than general.
Event Security
FGH Security, Sword Security and Showsec were among the event-focused businesses considered during the wider research.
Event security should be assessed separately from corporate guarding because crowd management, venue access, stewarding and large-event operations present a very different risk environment.
Keyholding
Security Keyholding Ltd is another London specialist worth considering for businesses primarily interested in alarm response, keyholding and mobile patrols.
Corporate London Security
United Guarding and SmartSec were among the London-focused corporate providers included in our wider research.
These businesses may deserve a shortlist position where local account management and commercial-property experience are more important than national scale.
Retail Security
Retail environments introduce different risks, including theft, customer interaction, loss prevention, employee safety and high footfall.
This makes retail experience more important than simply choosing the largest guarding company.
Construction Security
Construction sites can contain valuable machinery, tools and materials while layouts and access points change throughout a project.
Security may therefore combine guarding, mobile patrols, CCTV, perimeter protection and access control.
For wider market context, see our Construction Companies in London guide.
Close Protection
Close protection requires particular care when comparing companies.
A business advertising executive-protection services is not necessarily the same thing as holding ACS approval for Close Protection.
ACS is voluntary, so buyers should assess both the company and the licences held by the individuals who will actually perform the work.
What Does SIA Approved Contractor Status Actually Mean?
The SIA makes an important distinction:
it licenses individuals and approves companies.
Its Approved Contractor Scheme is voluntary.
A business participating in ACS is assessed against the relevant standard, but approval covers specific security activities.
That means buyers should not simply ask:
“Is this company SIA approved?”
A better question is:
“For which security activities is this company currently approved?”
A supplier approved for Security Guarding may not have approval for Door Supervision or Close Protection.
That distinction can be directly relevant to the contract being purchased.
Do You Need Physical Security or Cyber Security?
Physical-security providers protect people, property, sites, events and physical access.
Cybersecurity companies protect networks, systems, software and data.
A modern London organisation may require both.
A security officer controlling access to a building cannot replace penetration testing or incident-response capability for compromised IT systems.
Likewise, cybersecurity software cannot physically secure an office entrance or respond to an intruder.
Businesses evaluating digital threats should separately compare Cyber Security Companies in London.
How Much Do Security Companies in London Charge?
One of the clearest findings from researching the market is that major security providers generally cannot be compared fairly using one universal hourly rate.
This is why a statement such as “London security costs £15–£30 per hour” can be misleading without explaining the service specification.
How to Compare Security Quotations Properly
The correct method is to issue the same security specification to several companies.
If one provider quotes for a basic officer while another includes management, patrol verification, relief cover, monitoring and reporting, their hourly rates are not directly comparable.
Compare what is included as carefully as the total price.
What Should You Ask Before Hiring a Security Company?
Start with the precise service being purchased.
Check which ACS activities the business currently holds and whether personnel carrying out licensable work hold appropriate individual SIA licences.
Establish whether the work will be delivered directly or subcontracted.
Ask who supervises officers and how performance is monitored.
Find out what happens when a regular officer is absent.
For alarm response, determine who receives alerts, what escalation procedure is followed and how attendance is charged.
For multi-site contracts, ask whether service standards and response arrangements are consistent across every location.
For specialist environments, request examples from genuinely comparable contracts rather than accepting a generic client list.
Security Company Red Flags
A low price is not automatically a warning sign, but a quotation that cannot explain staffing, supervision, relief cover or escalation procedures deserves closer examination.
Buyers should also investigate vague accreditation claims, outdated certificates and unusually broad promises with little supporting evidence.
Another warning sign is an inability to explain incident escalation.
Security is most valuable when something goes wrong.
A supplier should be able to explain what happens following an alarm, intrusion, confrontation, officer absence or other significant event.
Should You Choose the Largest Security Company?
Not automatically.
Scale offers potential advantages such as management infrastructure, relief staff, technology investment and multi-site capability.
Smaller companies can sometimes offer closer account management, greater local knowledge or deeper expertise in a specialist niche.
The correct choice depends on the risk.
A multinational organisation occupying several major buildings may value the infrastructure of Mitie or G4S.
A Central London property operator could reasonably investigate CIS or Ward.
A business requiring nationwide alarm attendance may find The Keyholding Company’s operating model more suitable.
An airport or live event creates an entirely different shortlist.
Final Verdict
The biggest mistake when searching for the best security companies in London is assuming every provider is competing to solve the same problem.
They are not.
Our review of 50 providers found businesses designed around fundamentally different security models.
Mitie leads our overall shortlist for integrated security.
CIS stands out for corporate and London property environments.
Corps is particularly interesting where monitoring complements guarding.
G4S offers substantial scale.
Bidvest Noonan becomes relevant when security forms part of wider facilities management.
Wilson James and ICTS bring specialist aviation expertise.
Securitas combines physical and electronic protection.
Ward offers a compelling commercial-property proposition.
The Keyholding Company provides a specialist alternative when a business needs response rather than permanent on-site officers.
The correct buying process therefore begins with the risk, not the ranking.
Define what is being protected, determine when protection is required and decide where human intervention is essential versus where monitoring or technology may be more efficient.
Then compare several providers against the same specification and independently check current regulatory information before signing a contract.
That gives London businesses a much better basis for choosing a security provider than star ratings, promotional claims or company size alone.
Frequently Asked Questions
What Is the Best Security Company in London?
For large integrated security requirements, Mitie is our number-one overall selection for 2026.
That does not make Mitie automatically best for every requirement.
Specialists may be more appropriate for aviation, events, keyholding, construction or other specific security needs.
How Many Security Companies Did Companies.london Review?
Our 2026 research pool contained 50 providers, ranging from multinational contractors to specialist London firms.
Ten were selected for the main comparison, while others were retained as longlist or specialist candidates.
Are Security Companies Required to Be SIA Approved?
No. Participation in the Approved Contractor Scheme is voluntary.
ACS relates to businesses, while SIA licensing separately applies to individuals undertaking relevant licensable activities.
How Do I Check a Security Company’s ACS Status?
Use the current SIA Register of Approved Contractors.
Do not rely exclusively on a badge displayed on a company’s website.
Check both the company and the activity for which approval is held.
Which London Security Company Is Best for Offices?
CIS Security, Corps Security, Mitie, G4S, Securitas and Ward all merit investigation depending on the building and contract size.
Premium offices may require a combination of guarding, access management, visitor interaction, monitoring and emergency response.
Which Company Is Best for Keyholding?
Our specialist selection is The Keyholding Company, because keyholding and alarm response form the core of its business model.
Which Security Companies Are Strongest for Aviation?
Wilson James and ICTS stood out in our research because aviation and highly regulated environments form important parts of their operations.
Which Security Companies Are Best for Events?
Event buyers should assess specialist providers separately from general corporate-security firms.
FGH Security, Sword Security and Showsec were among the event-focused companies included in our broader research.
Is ACS Approval Enough to Choose a Security Company?
No. ACS status is useful evidence, but procurement should also consider relevant experience, staffing, supervision, references, technology, resilience and the exact contract specification.