What happens during security vetting and why did Peter Mandelson fail his?

Almost all officials working in Foreign Office HQ undergo process before gaining access to top secret material

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.