David Cameron made clear earlier this week that the constitutional niceties are only one consideration when it comes to the question of who should be running Britain: "There is convention and there is practice and they are not always quite the same thing."
He was hinting strongly that if Gordon Brown tried to cling on to power he would not necessarily be prepared to accept the rules laid down in Britain's "unwritten" constitution.
The guiding principles of what happens in a hung parliament were updated this year by the cabinet secretary, Sir Gus O'Donnell. His Cabinet Office manual is designed to buy the politicians enough time to strike a cross-party deal that will stick long enough to ensure a "strong and stable" government. That includes ensuring that the business of government goes on and can cope with everything, up to and including a full-scale sterling crisis.
But it is already clear that the party leaders interpret the rules in their own way. Brown believes it gives him the right to stay in Downing Street to negotiate a deal, Clegg used them to enter into talks with the Tories first, while Cameron has hinted he will ignore them altogether and go it alone in a minority government.
The manual's first rule for hung parliaments states: "Where an election does not result in a clear majority for a single party, the incumbent government remains in office unless and until the prime minister tenders his resignation to the monarch. An incumbent government is entitled to await the meeting of the new parliament to see if it can command the confidence of the House of Commons or to resign if it becomes clear that it is unlikely to command that confidence."
Gordon Brown's announcement that he had authorised O'Donnell to dispatch four-strong teams of civil servants to each political party to facilitate the talks triggered the start of that process this morning. In theory, at least according to the Cabinet Office manual, he could have until 25 May – the day set for the state opening of parliament – to stitch together a possible deal with the Liberal Democrats and whatever other minority-party MPs he needs to get a Commons majority.
But in practice, Ruth Fox of the Hansard Society has pointed out, the direction of public opinion, the response of the markets and the 24-hour news cycle are all likely to demand a far quicker resolution.
The opening gambit came when Clegg declared that it was for the Conservatives to have the first go at trying to form a ruling coalition. Brown said he "respects" their right to do that but reminded them he was prime minister and, if their negotiations failed, he wanted to talk to Clegg.
But as the former head of the civil service Sir Richard Wilson told his Cambridge students last night, Cameron and Clegg are both wrong to dispute Brown's right to remain prime minister.
"They're wrong for the very good reason that Mr Brown is prime minister. You can't change it, it's a fact. The Queen asked him to be prime minister, and until he resigns, he still is the prime minister. We don't elect a prime minister in this country. All anyone elects is their MP, and it's the MPs who decide who they will give their backing to as prime minister, that is the decisive factor."
Wilson, now master of Emmanuel College, Cambridge, said that as PM Brown has the "first shot at forming a government" which, in the absence of an overall majority, he could do by asking the Lib Dems if they will support him. "If they negotiate with him – which Nick Clegg seems to say he won't – until he tries that out, he's still entitled to be in the job," Wilson said.
From this view, Clegg's attempt to open negotiations with Cameron could be seen at least as a breach of the spirit of the rules. But there is no constitutional bar on anybody talking to anybody else, which Brown acknowledged in his statement today. So Clegg could, in theory, be talking to Cameron and Brown concurrently, leading to two competing coalitions depending on the precise arithmetic.
The O'Donnell rules also say that while Buckingham Palace is to be kept informed of what is going on, "the monarch would not expect to become involved in such discussions". In other words the most important thing is to keep the Queen out of it.
Instead the rules say that Brown is entitled to wait until the meeting of the new parliament – 25 May – to see whether he can put a majority together for his Queen's speech.
Cameron's intention to form a minority government sidesteps this measured process. He hopes that the sheer weight of political momentum, media and market pressure and the moral authority of leading the largest party will eventually force Brown to concede defeat. Fox says it is ultimately the politics of the situation that will dictate the outcome: "The PM has the right to try to form a government first but, as [Ted] Heath found, success is not guaranteed … Patience is as likely to be as effective as constitutional confrontation."
In 1974 Harold Wilson bided his time while Heath failed to strike a deal with the Liberals or the Ulster Unionists. After four days Wilson was at the head of a minority government, albeit one that did not last more than eight months. The failure to form a coalition in the next few days could well mean a second election sooner rather than later.
