programme with the then Home Secretary was his parliamentary private secretary Siobhain McDonagh, the MP who triggered the latest bout of speculation about a Labour leadership election by asking for nomination papers to be sent to Labour MPs.

(It's also worth noting that Joan Ryan, another MP to ask for nomination forms, was a junior minister under Reid at the Home Office, and that Waheed Alli, the Blairite peer implicated in the coup, used to be an adviser to Reid.)

Friends of Reid and McDonagh seek to hose down the idea of a move against Brown by his fellow Scot. There is no plot, they say, and the challenge to Brown must come from younger men, although one adds intriguingly: "John would make a marvellous deputy, a bit like Joe Biden".

McDonagh claims Reid was not aware of the letter she wrote, but admitted that she received a telephone call from him after the news broke on Friday night. "He was interested in how I was," she said. "He knows how this works."

The talk of a stalking horse - even a stalking stallion - underlines one of the difficulties facing Brown's opponents. Under Labour's rules 70 MPs are needed to back a candidate who is willing to stand. None of the Cabinet Ministers touted as potential leaders – David Miliband, Alan Johnson, Jack Straw – has shown any willingness to take that risk.

Reid, now chairman of Celtic FC, has said that he plans to step down as an MP at the next election. But he can easily renounce that decision - and he could afford to take the risk.

He’s not associated with the Brown regime; he’d make an able leader in the Commons for however long Labour can hang on - in fact he would give Cameron a run for his money; most important, the leadership wouldn't be 'wasted' on him if he lost the next election, as it most likely would be on a younger man if the Tories win by a landslide. Which they surely will if Brown remains leader.