After Keir Starmer announced Peter Mandelson as his pick to be ambassador to the US in December 2024, officials in the Foreign Office contacted him to organise the security vetting clearance process.
As with almost all of the 8,000 officials working in the Foreign Office’s Whitehall headquarters, Mandelson required a level of clearance known as developed vetting(DV). This is necessary for individuals in roles that require frequent and uncontrolled access to material marked top secret.
The vetting process is not carried out by the Foreign Office. It is done by security officials who work for United Kingdom Security Vetting (UKSV). It has been mistakenly reported that such vetting is carried out by MI6. That is not the case.
UKSV is an agency in the Cabinet Office and its vetting process is not to be confused with checks made before Mandelson’s appointment was announced, carried out by a separate propriety and ethics team. That due diligence process warned of a “general reputational risk” in appointing Mandelson in December 2024.
Weeks later, in late January 2025, UKSV concluded that Mandelson should not receive DV, but the Foreign Office decided he could receive that security clearance, which was necessary for him to take up the role in Washington.
The reasons why Mandelson failed the UKSV process have not been made public and details of an individual’s DV results have never been disclosed publicly before. Here’s what we do know about the UKSV process.
What happens during the security vetting process?
Some details are published by the government about the process. Applicants have to complete questionnaires on their use of the internet, their finances and any security considerations. Checks are made against security services systems.
Perhaps the most intense and intrusive section of the process is an hours-long interview with a security vetting officer, who will discuss a range of matters with the applicant. This could include their family, friends and associations, business relationships, sexual history, and alcohol and substance use. Questions are asked about travel, residences and citizenships.
The overall process normally takes months, but departments are able to nominate a small percentage of applicants for an expedited process by putting their candidate at the top of the queue. This appears to have happened with Mandelson.
The outcomes of the process include clearance being granted, clearance being granted with caveats and restrictions, or clearance being denied. In Mandelson’s case, clearance was denied.
Why might someone fail the security vetting process?
The process is all about managing risks. Applicants are told it is “vital to be open and honest throughout”, even about embarrassing material.
Two types of risk are considered. The first is of blackmail or coercion, some hidden information that could be leveraged against the person to force them to release sensitive material. The second is that the applicant is engaged in risky activities that could lead to them divulging sensitive information.
Security clearance can be withdrawn at any time if conduct, personal behaviour or other personal circumstances cast doubt on an individual’s reliability.
In Mandelson’s case, however, even though UKSV advised he should not be given clearance, the Foreign Office appears to have decided any risks that were identified could be managed and that he could take the role in Washington.
Did Mandelson receive any other clearance?
Days after Mandelson failed the UKSV process, the Foreign Office told him the role in Washington required an additional level of clearance, called DV+STRAP. This would require a new application to be made.
STRAP clearance – or “indoctrination” – is required for access to documents even more sensitive than top secret, such as intelligence material. Such documents are reportedly printed on pink paper to visually identify them.
It is unclear whether or not Mandelson received STRAP clearance. Given UKSV’s conclusion that Mandelson did not clear the barrier of DV, for him to receive an additional level of clearance would be extraordinary. Documents that may address this question are expected to be reviewed by the intelligence and security committee of parliament, which will face pressure to release them to the public.