Newly declassified documents have shed significant light on the controversial appointment of Peter Mandelson as the UK’s ambassador to Washington, revealing that he received sensitive security briefings and engaged with senior intelligence figures, including the head of MI6, before completing his developed vetting process. This premature access, alongside Mandelson’s initial belief that his status as a privy councillor negated the need for vetting, has intensified scrutiny on Prime Minister Keir Starmer's political judgment, a decision Starmer has since expressed regret over.

The documents, released through the humble address process, detail how Mandelson and Richard Moore, the former chief of MI6 (known as “C”), agreed to a meeting in early January 2025, prior to Mandelson's departure for Washington. He was not granted full security clearance until two weeks later. Furthermore, emails indicate Mandelson had already met with “Q,” Blaise Metreweli, the head of MI6’s technology branch and now the agency's overall chief, also in early January. Intelligence officials expressed a desire to leverage Mandelson’s presence for broader briefings on critical topics such as Russia and Ukraine, China, counter-terrorism, cybersecurity, and the Middle East, even as he was still declaring his extensive ties to figures in Russia, China, and Israel, including sanctioned individual Oleg Deripaska, to vetting officials.

Mandelson’s aide informed MI6 that while he had not yet received developed vetting (DV) clearance, he had been granted access to “higher classification material on a case-by-case basis,” leaving it to senior MI6 officials to determine appropriateness. The documents, however, do not conclusively confirm whether these specific meetings with 'C' and the planned security briefings ultimately took place. Vetting officials faced considerable challenges in gathering information on Mandelson due to the vast breadth of his contacts, prompting him to question if they required details of “literally every foreign national” he had ever met, ultimately being instructed to provide individuals with whom he had “personal friendships” or “personal business connections.” One senior official noted the difficulty, stating, “This is crazy. He knows EVERYONE!! They need to go ahead with the interview.”

The 1,500-page release, while extensive, notably withheld crucial documents, leaving many questions unanswered and raising concerns about transparency. Documents deemed “prejudicial to UK national security or international relations” were redacted by the intelligence and security committee (ISC). Specifically missing were details about measures taken to mitigate serious security concerns – which the Guardian previously revealed included his associations with senior figures in China, Russia, and Israel, and a £1 million loan. Additionally, evidence to support claims that the vetting body considered him a “borderline case” was absent. A nine-page summary compiled by UK Security Vetting (UKSV) was withheld at the request of the Metropolitan police, who cited potential future prosecution, further requesting the holding back of emails between Morgan McSweeney and Mandelson concerning his links to convicted child sex offender Jeffrey Epstein, and messages to Starmer’s former chief of staff.

Adding to the controversy, Mandelson “declined to comply” with a request to surrender his personal phone and allow the government to publish WhatsApp messages and other information pertinent to his appointment. His declarations of interest form, designed to detail commercial conflicts, was also withheld by the police. The documents further revealed embarrassing internal Labour criticism of Keir Starmer, with Mandelson himself stating the prime minister tended to buckle under pressure and lacked verve. This contentious appointment has had significant repercussions, contributing to the departure of Starmer’s chief of staff, Morgan McSweeney, and the top official at the Foreign Office, Olly Robbins. Darren Jones, the prime minister’s chief secretary, informed MPs that some messages between Mandelson and ministers were unavailable due to disappearing messages or device changes, with a parliamentary debate on the documents scheduled.