In office - but not in power

“Never glad confident morning again.”

These words, from a poem by Robert Browning, are the harbinger of doom for Prime Ministers. There comes a point in almost all administrations, when authority dies, sometimes suddenly, but more often it is squeezed out, like the last drop of toothpaste from a tube. The seemingly impregnable Downing Street fortress becomes a besieged city, with rations of political capital running short.

Sometimes Prime Ministers remain, in the hope that it will turn into Mafeking, that after months of resilience, relief will come. But it never does.

In the post war era, the rapid deflation of power affected Eden, who was sunk by Suez and had to go within a few months; while Macmillan was undone in an instant by the Profumo affair and again only survived a short time. Both had seemed so powerful before. The suave Eden with film star looks, who had been for so long Churchill's heir; and Supermac, the man who was able to say truthfully “you have never had it so good”. Both found how transitory power really is.

They are not alone. Blair lost his authority more gradually over the Iraq war, but more particularly when he was forced by junior office holders to set a date for his departure. Brown was finished over a single weekend after the Labour Party Conference in 2007, when he pretended that an early election that he was expected to call shortly after succeeding Blair was never really planned, and that he had not taken any notice of the opinion polls. The truth was that George Osbourne’s promise of a £1 million threshold for death duties moved the polls against him, and made it look unlikely that he would win an outright majority. This modest political inaccuracy undid his reputation as a dour but honest politician, and the subsequent financial crisis made his time in office one of frustration.