Did a new constitutional rule emerge in Britain in May? Was this an establishment coup?  Peter Osborne asks the latter question in a review of four books in the London Daily Telegraph (2/12)

The most detailed he says  is Five Days to Power (Biteback) by  Rob Wilson, a Tory MP who  gained access to most of the participants, including David Cameron and Nick Clegg (though not Gordon Brown). The result he says is a first-class piece of journalism, full of shrewd judgments and new information.

He reveals that Sir Gus O’Donnell, the cabinet secretary, prepared for a hung parliament, producing a new cabinet manual, entitled “A Compendium of the Laws, Conventions and Constitutional Underpinning of the UK System of Government”.

He says the practice hitherto was that if an election failed to provide a decisive result the monarch invited the incumbent prime minister to seek to form a government. If he failed, he would resign, at which point the leader of the opposition would be given a chance.

…novel convention…

 Sir Gus dumped this long-standing doctrine.

He replaced it with a novel convention, according to which the incumbent prime minister was required to stay on even if he failed to form a government until such time as a rival was capable of securing a majority of the House of Commons.

This change was kept secret at the time (although crucially Brown did sign off on it when the new codification was presented to him in the spring).

It was, however, to have momentous consequences. Under the traditional system, Brown would have been forced to quit Downing Street almost at once and Cameron would have found himself installed as prime minister by the weekend at the latest, as the head of a minority administration.

Rob Wilson writes: “This scenario raises an interesting ‘What if?’ question of history. Would Cameron have made his ‘big, open offer’ of a coalition to the Liberal Democrats if Brown was in the process of being forced out by media and public pressure and Downing Street was at his mercy? Would Cameron have been able to persuade the Conservative Party to pay the price of securing a coalition deal – the offer of a referendum on electoral reform – if he was already in Downing Street as prime minister?”

The answer: almost certainly not.

[continued]

But there was one loser from this arrangement – Brown. He became a prisoner in Downing Street, hanging on to the illusion of power while his rivals divided up the spoils of office.

Professor Osborne says that Anthony Seldon and Guy Lodge show in their biography, Brown at Ten  (Biteback), that this drove Gordon Brown “crazy.”

The authors tell “the astonishing story” of how Buckingham Palace, observing the new O’Donnell convention, refused the prime minister’s desperate requests to resign.

They say he was told to wait until Cameron and Clegg were ready to take power. Forced to stay in Downing Street against his will, “the hapless Brown could do nothing more than rage against this royal command, unprecedented in British history.”