LONDON, June 6 -- The handwritten note Peter Mandelson sent David Lammy in November 2024 reads like something between a job application and a promise. The government, he assured the then-Foreign Secretary, would "never regret" appointing him as Britain's ambassador to the United States. That pledge, released Monday as part of more than 1,500 pages of government files, has since become the defining emblem of the political catastrophe now consuming Keir Starmer's premiership.

The documents go further than any previous disclosure in exposing the contradictions at the heart of the Mandelson appointment. Most damaging is what they reveal about Mandelson's private posture toward the prime minister he was nominally serving. In a May 2025 WhatsA...