Olly Robbins, the Foreign Office’s top civil servant, has been sacked, purportedly for failing to tell the Prime Minister that Peter Mandelson had failed security vetting for the role of US ambassador. Yet it’s inconceivable that Robbins would have signed off on the Labour grandee’s developed vetting (DV) without first talking to 10 Downing Street.

Of course, Robbins is unlikely to be missed at the Foreign Office: the culture has been toxic since his arrival last year. His first blunder was to write to staff saying that if they didn’t like the Government’s Gaza policy, they could resign. It now turns out he ignored a United Kingdom Security Vetting (UKSV) recommendation that Mandelson did not meet the required standard for security clearance.

No current or former member of HM Diplomatic Service will be surprised that Mandelson failed his developed vetting. The 11 March volume of Government documents about his appointment as ambassador to Washington showed Downing Street to be dismissive of the fact that, as a Cabinet minister, Mandelson stayed at Jeffrey Epstein’s US home while the sex trafficker was in prison. That was shortly before a photo emerged of Mandelson, Epstein and Andrew-Mountbatten Windsor together. Or the underpants shot.

The flinty-faced former cop working for UKSV who conducted Mandelson’s two-hour vetting interview clearly concluded that he wasn’t of sufficiently “reliable” character to be entrusted with access to “Top Secret” intelligence material. Robbins nevertheless ignored the recommendation, signing off Mandelson’s DV. What has raised suspicions is that Robbins was brought in as a yes-man to address Keir Starmer’s concern that the Foreign Office was drowning in the “tepid bath of managed decline”. Now he has been sacked just as the Prime Minister is clinging desperately to his job.

Right from the start, Starmer has resorted to bluster. First, he clung to the so-called “due diligence” process when eyebrows were raised over Mandelson’s appointment. The 11 March document dump proved that the process had been a sham, nodded through by the No. 10 Director of Communications Matthew Doyle, a friend of Mandelson who had campaigned for a known paedophile in a Scottish council election. The King’s approval — a requirement for all ambassadorial appointments — was shunted through in a day.

There’s a reason most people pass DV clearance. Joining the Diplomatic Service is such a competitive and extended process that by the time it comes to vetting, the organisation has a decent idea of what’s under the hood. Mandelson faced none of the correct scrutiny because he was given the job in a hurry by Starmer, who had dithered for months after shoving Tim Barrow, Britain’s former ambassador to Moscow, to one side.

Another purpose of DV is to provide comfort to the UK Intelligence Community about an officer’s “reliability”, given that spooks and diplomats work together seamlessly, both in London and overseas. Mandelson would have been briefed by the MI6 Head of Station regularly and would have known the identities of some of the intelligence officers at post.

DV clearance only ensures you can work for the Diplomatic Service. Diplomats can’t read actual intelligence material until they have received STRAP clearance, which is awarded by the UK Intelligence Community. As the US is the UK’s primary intelligence relationship, Mandelson may potentially have had access to intelligence material related to every key country, including Russia, China and Iran.

The trouble is that the nation’s spies take their cue from the FCDO in deciding whether to award STRAP. If they awarded Mandelson STRAP clearance on the basis that he had been given a clean DV by Robbins, then Starmer has a much bigger problem.