It was one of those moments you never forget. "Gordon's gone," my wife said as I walked in the front door. "He's resigned." From the television somewhere behind her, the familiar Scottish brogue echoed through the house. "I have led this country for almost 13 years," he said. "Ten of them as chancellor, and three as prime minister. When I won the last election, I made up my mind to retire sooner rather than later. My work is done; it is time to hand over the baton."

On the evening that Gordon Brown decided to call the 2007 snap election, we now know, he told his closest aides that if he won he would serve only two more years. He had no intention of going down in history, he said wryly, as "another Tony Blair". He would set a bold agenda for the 2010s, then step gracefully aside.

Few doubted that Brown would win; the only question was the size of his majority. Even so, most observers were amazed when, celebrating a 21-seat victory, this most tribal of Labour politicians announced that he had invited the Liberal Democrat leader, Menzies Campbell, to join a centre-left coalition. "It is time," Brown said, "to heal the progressive divide."

What followed was six months of stunning political drama. As the banks tottered and the world economy tumbled into recession, Brown and Campbell set out a breathtaking agenda of modernisation. At the Treasury, Alistair Darling and his chief secretary, Vince Cable, devised

a rigorous new regulatory regime, while Harriet Harman and Nick Clegg worked out a programme of constitutional reform, cleaning up MPs' expenses and introducing limited PR. There was even a place for Lembit Öpik as minister for fun, though his idea of fun never seemed quite the same as anybody else's.

Meanwhile, the Labour left and the Tories were in uproar. A dozen Labour MPs resigned the party whip in protest at Brown's coalition, although, the cushion of Lib Dem numbers meant they were barely noticed. As for the Tories, Cameron learned the hard way what his predecessors had known: there is no party in the western world so quick to punish failure. Back he went into obscurity; back came William Hague as leader of a more aggressively Thatcherite, Eurosceptic party than ever.

In stepping down so smoothly, Brown showed the same vision and decisiveness that compelled him to seek a national mandate in 2007. We can only hope our new Prime Minister has the same qualities. Over to you, Ms Harman . . .