Morgan McSweeney, Keir Starmer's former chief of staff who resigned earlier this year over the scandal, has confessed to MPs that he pressured Foreign Office officials to fast-track Peter Mandelson's appointment as UK ambassador to Washington. But he insists he never asked anyone to 'skip steps' in security vetting - merely to move with the kind of urgency usually reserved for a burning building or a free bar.

In a rare appearance before the foreign affairs select committee on Tuesday, McSweeney acknowledged asking the then top Foreign Office official, Philip Barton, to conduct the process 'at pace,' but denied any impropriety. 'There is a real difference between asking people to act at pace and asking people to lower standards. We never did that,' he said, presumably while maintaining eye contact with everyone in the room.

McSweeney insisted he wasn't involved in Mandelson's vetting process, nor did he ask officials to 'ignore procedures, request that steps should be skipped or communicate explicitly or implicitly that he should be cleared at all costs.' That would have been 'unacceptable,' he said, as though there's an acceptable way to ask someone to skip vetting steps.

His testimony came after Barton told MPs there 'absolutely' was pressure from Downing Street over the pace of vetting. Olly Robbins, Barton's sacked successor, had previously told the committee he felt 'constant' pressure to get Mandelson into post - presumably the kind of pressure that makes you wish you'd chosen a career in accounting.

McSweeney revealed that learning the extent of Mandelson's ongoing links with Jeffrey Epstein - after he had been questioned about red flags raised during due diligence and sent to Washington anyway - was like a 'knife through my soul.' Whether that was a knife of shame or just embarrassment at having to answer for it remains unclear.

He admitted he should have asked civil servants in the Cabinet Office's propriety and ethics team (PET) to seek clarification with Mandelson, rather than doing so himself, given their relationship. 'When I look back on it, I certainly think it would have been much, much better if I'd asked PET to ask those follow-up questions,' he said, adding that he thought Mandelson would 'feel more obligated to give truth and the full truth' in writing. Spoiler: he didn't.

McSweeney said Starmer would not have gone ahead with the appointment had he known the full truth. 'The prime minister did not have enough information because Mandelson did not share the necessary information with him. He had ample opportunity to do so and did not.' So much for that vaunted political cunning.

He acknowledged that withdrawing Mandelson's appointment over his failure to get security clearance would have been 'embarrassing' for the government, but 'far preferable' than allowing it to proceed. Many Labour MPs are reportedly angry that Downing Street, aware at the time that Mandelson was close enough to Epstein to stay overnight at his house, decided to send him to Washington anyway.

McSweeney admitted he had made a 'serious error of judgment' in advising Starmer to appoint Mandelson, but claimed he had felt his 'experience, relationships and political skills' - including on trade - could serve UK interests as Donald Trump re-entered the White House. Because nothing says diplomacy like a friend of a convicted sex offender.

In his own evidence, Barton said No 10 seemed 'uninterested' in the vetting process, and that there were no avenues for him to express his concerns. Asked if he was under pressure to get the vetting done quickly, he said: 'Absolutely… I don't think anyone could have been in any doubt in the department working on this that there was pressure to get everything done as quickly as possible.'

Barton denied having received any phone call from McSweeney - long rumoured - which had asked him to 'just fucking approve it.' McSweeney told MPs that such Westminster rumours were 'corrosive' to faith in the political system, which is rich coming from a man who just admitted to pressuring officials.

Barton, who left the Foreign Office in January, said he was unaware of No 10's intention to appoint Mandelson until a day before the announcement. 'I wasn't involved, I wasn't told a decision was coming,' he said, suggesting the news came as a surprise akin to finding a dead fish in your mailbox.

He told the committee that his concerns about Epstein were shared by the national security adviser, Jonathan Powell. But he said the 'die was cast' and there was no possibility of advising against the appointment. He noted it was unusual to announce the appointment before vetting had been completed - a procedural step the government apparently deemed optional.

Barton said he had been in discussions with former ambassador Karen Pierce about extending her appointment, but was presented with the Mandelson appointment 'and told to get on with it… There was no space for dialogue.' He also said he was well aware of the 'toxic' nature of the Epstein connection from his time in the US, and worried it could become a problem. Spoiler: it did.

He said there was 'no space or avenue or mechanism for me to put that on the table,' even though he was aware of tweets from those close to Trump reminding the incoming president about Mandelson's negative comments about Trump. Asked if Number 10 was 'dismissive' of the vetting, Barton said: 'The word I would use is uninterested.' Which, in diplomatic terms, is roughly equivalent to saying 'they didn't care at all.'