Peter Mandelson was always a high-risk appointment – his departure will not end the matter for Keir Starmer

The line between pulling off a diplomatic masterstroke and setting up an accident waiting to happen can be a fine one. In the seven-month fable of Peter Mandelson’s UK ambassadorship to the US, the crossing of that line has created a political polycrisis for which it is hard to think of a parallel.

In the week after the prime minister, despite his efforts, lost his deputy, and the week before the American president arrives in the UK for an unprecedented – and unpopular – second state visit, Keir Starmer, despite his efforts, has lost the person he controversially personally appointed to the UK’s highest diplomatic post. Worse, over a matter that also happens to implicate Donald Trump – a matter journalists could conceivably raise at the president’s and prime minister’s press conference during the forthcoming state visit.

The risk in the main was in the ambassadorship itself. The US is the UK’s closest and most important international ally and the Washington ambassador is the lynchpin of that relationship. They are the UK’s eyes and ears, permanently operating at the centre of the political and social life of the US capital in the way that no other country’s ambassador has been, is, or could be.

But the risk was also in the man. Prince of Darkness, Third Man, (only last week: “my familiar role as professional villain”), possessed of a public career already involving two high-profile reputation-wracking resignations, Mandelson has always been weapons-grade Marmite.

It was a reflection of post-Brexit British weakness, rather than strength – the desperate need for a trade deal – that Starmer turned to him. Yet personal relations being so important with this president, it can now be seen to have made less sense to have replaced a scandal-free ambassador – Karen Pierce – who was on the best possible terms with Trump and his people. She may return.

Its prominence is why, perhaps, DC is usually the only British ambassadorship that is ever “political” – that is, that a prime minister personally chooses someone who isn’t a diplomat. And even then, it’s rare. One may now see now why. The previous political appointment – in the 1970s – also ended inauspiciously, in a welter of recriminations over nepotism and extra-marital affairs resulting in best-selling novelisation and a hit movie.

The main grounds for Mandelson’s appointment were his public prominence (his “weight”), his experience as an EU trade commissioner, and his almost preternatural networking skills. The latter has been his undoing, given that for years he networked with the man who was to become the world’s most infamous sexual abuser of children.

To describe the appointment as high risk and high reward matters because of the supreme importance of the office and the singular character of the officer. If one can screen the Epstein stain momentarily, the widespread frustration in government was that Mandelson had been justifying that risk.

He was clearly an effective ambassador. Only the week before he delivered a trenchant statement of the contemporary special relationship; the day before he was sacked he had spent an hour with Trump. Ambassadors tend not to have meetings with presidents.

Fundamentally this falls on the fallen. Mandelson knew of the Epstein material that has come to be made public, knowing that it might be made public. He admitted only this week that even more was likely to come after the initial, highly embarrassing, disclosure.

Mandelson took the UK’s most important diplomatic post knowing he was sitting on a ticking bomb. Given the precise nature of the explosive, the political obituary can certainly now be written about one of the most vivid public figures of the past 30 years.

But the more consequential damage will be to the man who appointed him. Downing Street’s statement that security vetting took place without its involvement is not credible.

Much may hinge on what the vetting files reveal – if they are revealed. The decision on whether to release them is a matter for MPs, and how Labour backbenchers choose to vote will be a significant indicator as to the mood in the party.

A crisis from Hades, replete with shadowy associations of global elites and paedophile rings; a hot buffet for online conspiracists, who may be more numerous and prominent in the US, but are far from reticent in the UK. And so the political class undergoes another detention.

The political damage to the government in general and to the prime minister in particular is hard to overstate. That is in part a matter of misfortune: that this particular major crisis comes a week after the previous one. But it has nevertheless provided the leader of the opposition with the most palpable success of her own benighted tenure. Seldom can a relaunch have relapsed so quickly.

However hapless he may increasingly appear, it’s too early to write Starmer’s political obituary. The election may be over three years away, his parliamentary majority is unassailable, and his party – unlike that of the leader of the opposition – has no culture of regicide (although mayor Andy Burnham, observing and pronouncing from Manchester, seems increasingly prepared to test that). Yet the very size of that majority, and the near certainty that many Labour MPs will be one-term, makes public expressions of discontent consequence-free, and consequently freer.

It’s more than curious that so innately risk-averse a person as Keir Starmer appointed so risk-taking a person as Mandelson to his country’s highest-profile international office. That misgivings were aired at the time, including in these very pages, is the least of it.

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Martin Farr does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.