The mastermind behind Labour’s landslide victory has fallen on his sword. Morgan McSweeney has resigned as Prime Minister Keir Starmer’s chief of staff, taking full responsibility for the disastrous appointment of Peter Mandelson as US Ambassador.

In a dramatic Sunday shake-up at Downing Street, the man credited with engineering Labour’s return to power has exited the stage. Morgan McSweeney, often described as the "brain" of the Starmer operation, released a resignation letter that was as blunt as it was final. He admitted that advising the Prime Minister to appoint Peter Mandelson was a "wrong" decision that has damaged the party and eroded public trust.

This resignation is a seismic event in British politics. It signals that the fallout from the Mandelson appointment—which has been dogged by controversies surrounding his past associations with Jeffrey Epstein—is far more toxic than Number 10 initially calculated. By stepping down, McSweeney is attempting to act as a firebreak, hoping to shield the Prime Minister from the encroaching flames of the scandal.

The Letter That Ended a Career

McSweeney’s resignation statement was a masterclass in taking the hit. "When asked, I advised the prime minister to make that appointment and I take full responsibility for that advice," he wrote. "In public life, responsibility must be owned when it matters most, not just when it is most convenient."

The "Mandelson Fiasco," as it is now being called, has dominated the headlines for days. The decision to send the former spin doctor to Washington was meant to leverage his connections, but it backfired spectacularly when scrutiny turned to his financial dealings and past friendships. McSweeney’s departure raises serious questions about the vetting processes at the heart of government.

• The Power Vacuum: McSweeney was not just an aide; he was the central architect of Starmerism. His exit leaves a gaping hole in the Prime Minister’s inner circle.
• The Epstein Shadow: The resignation letter explicitly mentioned the need to "remember the victims of Epstein," a line that underscores just how damaging the association had become for a Labour government that prides itself on moral rectitude.
• The Opposition's Glee: Conservative and Reform UK MPs have seized on the chaos, describing the government as "rudderless" and "amateurish" barely two years into its term.

Starmer’s Judgment on Trial

While McSweeney has taken the fall, the ultimate question remains: Why did Keir Starmer sign off on the appointment? The Prime Minister has accepted the resignation with "gratitude for his service," but the political damage is done. The narrative has shifted from a government delivering change to an administration mired in the sleaze and cronyism of the past.

For McSweeney, who spent years plotting Labour’s path out of the wilderness, this is a bitter end. He leaves Downing Street not in triumph, but as a casualty of one of the most controversial personnel decisions in recent memory. "The only honourable course is to step aside," he concluded—a rare moment of accountability in a political culture that often lacks it.