Jeffrey Epstein and Peter Mandelson, the paedophile and the peer.
It was a friendship that endured even beyond Epstein's convictions and one on Thursday that ended Lord Mandelson's political career.
Politics Live: Starmer accused of 'blatant disregard for national security considerations'
When emails emerged of exchanges between the two men showing Lord Mandelson remaining supportive of Epstein even after he was convicted for the sex trafficking of underage girls, it was clear he had to go.
Lord Mandelson tried to cling on. The PM summarily relieved him of his duties.
There had initially been an appetite to keep him, in order to avoid embarrassing Donald Trump, who himself is being asked questions about his association with Epstein - and hates it.
But when these emails emerged, it was clear to No 10 that the scandal would blow up the state visit and Mandelson had to go.
But what was also true was that even attempting to keep him in these circumstances could blow up Sir Keir Starmer.
The parliamentary party - and particularly many of the women MPs - were absolutely furious that Mandelson had backed a convicted paedophile against women and girls who had, to quote one victim, been passed to men by Epstein like fruit trays.
The spectre of a powerful man like Mandelson trying to protect him and even the thought of the PM trying to row in behind was absolutely unconscionable.
As Harriet Harman said on our Electoral Dysfunction podcast before he was sacked: "These young women talked about the ruination of their lives by this man abusing his wealth and his power.
"And the idea that Peter Mandelson sided with Epstein in that situation - and this is always the question - whose side are you on?
"You've got to be on the side of the vulnerable and not against the person who commits criminal offences, abusing their power."
Harman also said she thought the prime minister would have been in "anguish" over having to defend Mandelson in the Commons.
He looked almost as green as the green benches on Wednesday as he insisted he had full confidence in his ambassador, despite warnings from Mandelson himself that more embarrassing material was about to emerge.
When that material did emerge, I understand that the PM spent the evening in Downing Street going through the material and then summoned his new Foreign Secretary Yvette Cooper, who has been a tireless champion in the fight to end violence against women and girls, for a meeting in which they decided to sack Mandelson.
Read more:
No 10 appointed Mandelson despite concerns
Analysis - why wasn't Mandelson fired yesterday?
That the US ambassador didn’t go of his own accord has angered many MPs and probably the PM, who has a record of prosecuting child sex offenders and made halving violence against women and girls a priority for this government.
Now Mandelson has gone. But, with the end of that comes new questions.
Questions about Keir Starmer’s political judgement.
This is not the first time Lord Mandelson has resigned in disgrace.
He stepped down as trade secretary over a loan from a colleague he failed to register under Tony Blair, and then quit again as Northern Ireland secretary over a cash for passports scandal.
And now the question is, in light of the Epstein connection, why did Starmer let him back in?
There is talk around Westminster that his key advisers had backed the move and Starmer had some reservations.
As well he might, because in the end, the scandal of it all stops at the PM’s door.
There are questions as to whether No 10 ignored concerns raised by the appointment and Badenoch is asking for full transparency.
My colleague, Sam Coates, was told by two sources that the security services did flag concerns as part of the process.
It is not known whether all of the detail was shared with the prime minister personally.
The prime minister's official spokesman said No 10 "was not involved in the security vetting process".
Badenoch said the latest revelations "point yet again to the terrible judgement of Keir Starmer".
She added that it is "imperative that all documents relating to Peter Mandelson's appointment are released immediately".
Then there is a bigger picture.
Two weeks into a supposed reset, two scandals and two key figures gone from government.
This was a PM who promised to do politics differently and clean up after the scandal-ridden Tory years.
Peter Mandelson’s return to government and ousting in this manner casts a long shadow over the PM and that promise, and raises serious questions about the PM’s political judgement.
It also casts a shadow over the upcoming state visit.
It was only on Wednesday that No 10 was thinking about trying to keep Mandelson to try to avoid putting the spotlight back onto President Trump.
With the White House, Royal Family and the UK government all tarnished by association with sex offender Jeffrey Epstein, this was an issue they all wanted to avoid and now it is top of the agenda.
(c) Sky News 2025: Starmer ousted Mandelson quickly - but questions remain about his political judgement