1. Mandelson did not fully cooperate with the process

The so-called humble address motion that obliged the government to hand over documents was very broad but there are a few pieces of information missing. An early passage about the scope of searches said that on 31 March this year, a government official wrote to Mandelson, via his solicitors, to request “any information held on his personal phone”.

It went on: “Peter Mandelson declined to comply with this request. The government has no further recourse to search the personal devices of Peter Mandelson.”

2. Mandelson did not have much faith in Starmer’s government

Perhaps less new than illuminating as to how and why Mandelson felt Starmer’s No 10 was underperforming, with many insights coming from his voluminous WhatsApp chats with Pat McFadden, one of Starmer’s most trusted ministers.

Downing Street is “beleaguered and bereft”, Mandelson said after a visit there in July 2025. Later the same day he described the PM’s habitual style to McFadden as “advance/buckle/advance/buckle”. Starmer, he argued another time, “lacks verve, as does the cabinet as a whole”.

McFadden, it is worth noting, has uncomplimentary views of his own, saying of Labour MPs about his then-role in the Cabinet Office: “Every meeting I have is: ‘Who can we tax in order to pay benefits to others?’ They’re asking the wrong questions.”

3. Mandelson told David Lammy he would not regret the appointment

One item in the files is a handwritten note from Mandelson to David Lammy, then the foreign secretary, in November 2024, shortly before his role was confirmed.

Written on Mandelson’s own House of Lords paper, he hopes that Lammy has not found media speculation about the job “too irritating”. The note goes on: “I just wanted you to know that if you were to appoint me, I would make sure you never regret it.”

4. He was quite rude about Wes Streeting

The former health secretary was close to Mandelson in the past, to the extent that in February he pre-emptively released his own copies of their WhatsApp messages to try to limit any political damage.

In July 2025, Streeting was expressing alarm at Israel’s actions in Gaza, and was among cabinet ministers trying to push Starmer for the UK to formally recognise Palestinian statehood.

“By way, I received a wild long hysterical message from Wes about Israel,” Mandelson wrote to Pat McFadden, adding: “I pushed back. I can forward but reflects pretty badly on his maturity in my view.”

Days later, after Streeting had lobbied cabinet colleagues for more action over Gaza, Mandelson told McFadden: “I think Wes is experiencing an early mid-life crisis.” McFadden did not reply.

5. Mandelson said Starmer should meet John Major – and gave him campaign advice

Messages between the pair are notable for their brevity and formality – unlike many of the other exchanges, it was clear that Mandelson and Starmer were not close.

In late June 2024, shortly before the general election, Mandelson messaged the Labour leader about things he had “picked up strongly on [the] doorstep” in Bury.

Shortly after the election, Mandelson messaged to say he had had dinner with Major, the Conservative former prime minister, that evening “and if you don’t know him I think good idea to invite him for a chat. As well as being a very nice person, he is interesting and thoughtful.”

He added: “Just a thought. No need to reply,” which Starmer did not.

6. A lot of ministers messaged Mandelson to congratulate him

Many people in the government would like to think they always had at least some doubts about the wisdom of appointing so tarnished and controversial a character. But the actual WhatsApp exchanges instead show a string of messages of congratulations to the new ambassador, some definitely verging on the fawning.

“Congratulations your excellency. What a wonderful appointment,” said the then junior minister Ian Murray. Steve Reed, who was environment secretary at the time, said: “Excellent appointment.”

7. Mandelson really, really wanted to be chancellor of the University of Oxford

Mandelson was always known to have a voluminous contacts book, and in the months before his appointment to Washington he did his best to use it to secure another role – chancellor of the University of Oxford.

The cache of WhatsApp messages show many in which Mandelson lobbies large numbers of Oxford alumni he knows – and in some cases barely knows – in politics to ask they vote for him. These include a series to Ed Miliband, several of which receive automated replies, including one that says: “This number is no longer used regularly.”

At one point Mandelson checks with Streeting to see if he has the correct number for Keir Mather, a new Labour MP, someone else he lobbies who does not reply.

8. Donald Trump wanted a red box (which was not easy)

One of the lengthiest sagas in the correspondence is about manufacturing a “red box” for President Trump – a version of the red cases that UK ministerial papers are placed in, but with “President of the United States” written in gold on it where the ministerial post would usually go, to hand to Trump during his state visit to the UK in September 2025.

While there was consensus this was a good idea, by August, Mandelson and various other senior officials were in endless discussions about whether the chosen supplier would produce it in time.

By late August, with the visit looming, Mandelson was fuming. “Whitehall has known about since February and it was confirmed in early July and nobody had the wit to say anything. What incompetence,” he wrote to Morgan McSweeney, Starmer’s then-chief of staff.

Another message to McSweeney read: “This is like something out of Thick of It … I have gone tonto on this.”