Lord Peter Mandelson insisted the Foreign Secretary would “never regret it” if he was appointed US ambassador.
The disgraced Labour grandee wrote to David Lammy urging the Cabinet minister to give give him the UK’s top job in Washington.
The letter, written in blue pen on notepaper headed with Lord Mandelson’s name and a House of Lords seal, read: “Dear David, As today (and all week) is polling day in Oxford and I am returning to London, I wanted to drop you a line, personally, about Washington.
“Thankfully, the media speculation has gone away and I hope this was not too irritating to you. I just wanted you to know that if you were minded to appoint me I would make sure you never regret it.
“I fear that navigating Britain’s interests through the Trump administration will require super-human skills and luck and a massive team effort.
“There is so much riding on it, on security and defence, on trade and economy and on the relationship, not to mention China.
“If we all put our best minds and energy to it, I think we can pull it off but we have to be realistic.
“For me it would be the last thing I do in public life and it would be a huge honour to serve you and the Government in this role. So if you are up for it, so am I.”
It was dated dated November 18, 2024.
The revelation is part of more than 1,000 pages of documents on Lord Peter Mandelson’s appointment as UK ambassador to the US have been released by the Government.
The handwritten note to the then-foreign secretary came on in November 2024, a month before he was eventually appointed US ambassador.
The release of doucments includes previously classified papersand personal WhatsApp messages exchanged by the former ambassador with senior figures in the Government.
It is the second batch of files relating to Sir Keir’sill-fated decision to give the prestigious Washington post to Lord Mandelson rather than a career diplomat.
The peer was sacked in September 2025 just nine months into the job when more details emerged about his friendship with Epstein.
Subsequent revelations in the Epstein Files led to a Metropolitan Police investigation into alleged misconduct in public office.
No 10 indicated the release of documents was everything it planned to publish on Lord Mandelson, apart from files held back at the request of Scotland Yard to avoid jeopardising its investigation.