In a government famous for policy U-turns, it is highly unusual for a minister to be sacked or moved. Policies change, but ministers tend to stay put. The pattern will not save Liam Fox, the current subject of seething speculation, and nor should it. But the stability in relation to ministerial personnel means he has more of a chance to put his case, however unconvincing, than if he had been clinging on as a member of the previous government.
There has been no reshuffle of any significance since the election 17 months ago. The departure of David Laws soon after the Coalition was formed has turned out to be the exception rather than the rule. Vince Cable survived the disgraceful set-up by a couple of journalists in his constituency office, when he was recorded attacking Rupert Murdoch. Chris Huhne is still in place, the relationship between him and his driving licence (not to mention his tweeting) not yet barring him from office.
Ken Clarke left the Conservative conference to stride exuberantly back to his departmental office in spite of engaging in a dispute about a cat with Ms May, as well as having survived an earlier frenzy about the implications of his sentencing reforms in relation to rape. Andrew Lansley is still in place even though he has suffered the ultimate humiliation of unveiling a revolution for the NHS, only to be told to unveil it all over again.
Even now, the more forensic peers in the Lords recognise that at least one more unveiling is required to save the NHS from chaos. Lansley takes it more or less in his stride.
In the anti-politics age, the orthodox reaction is to dismiss such resolution as pure self-interest. The opposite is closer to the truth. David Cameron models too much of his leadership style on Tony Blair, but he has learnt from one of Blair's errors. Under New Labour's rule, planned reshuffles happened far too often, unplanned changes even more so. The constant switching of ministers was a significant factor in the failure of many to make their mark on departments, or more generally on the Cabinet when it had wider discussions, such as over the build-up to war in Iraq.
Blair also conceded far too easily when frenzies erupted in the media. Peter Mandelson should not have been sacked the second time. Geoffrey Robinson should not have been ejected the first time that Mandelson was sacked. Charles Clarke should have been kept at the Home Office.
On one of the days when Ken Clarke was the victim of such hysteria, a former adviser to Blair, John McTernan, said approvingly that Blair would have sacked the Justice Secretary. I suspect Blair would have carried out one major reshuffle by now. His first was in the summer of 1998, a year after the election.
Cameron faces different constraints. A coalition makes ministerial change far less attractive and on the whole he has most of the media on board without having to work quite so hard at pleasing them. Nonetheless it is a quality of his leadership that he tends to stand by ministers until the evidence is overwhelming.
The advantages of ministerial continuity are immense. Above all, ministers need time to acquire an authority within their department. Senior civil servants tend to regard their departments as personal fiefdoms visited fleetingly by precarious cabinet ministers. The officials are there for much longer, and security of tenure gives them a power that mere elected ministers can only dream of.
In the Cabinet Office, Francis Maude is the latest minister attempting to reform the civil service. Let us hope he succeeds because this is an institution in need of sweeping change. Many of his predecessors, however, have tried before without success. One change within the power of elected leaders is to keep a minister in place for long enough to get a grip.
The development of policy is also helped enormously if a single minister remains for more than a few months. On average, Labour had a new Transport Secretary every 12 months. The arrival of another one was more dependable than the trains for which they were theoretically responsible. To some extent, Blair's public-service reforms were also undermined by constant ministerial changes. In contrast, some of the ministers in the Coalition are starting to display a degree of confidence and authority – at least within their departments and sometimes at Cabinet meetings.
The case of Fox is different from some of those colleagues who were fleetingly vulnerable. Mostly the others were one-day wonders. This is a saga without immediate resolution, with the interim report on his conduct being no more than a holding operation. In the meantime, speculation will intensify, a destabilising activity that feeds on itself. In the end, Cameron's judgement must rely on the facts when they are established and I sense that is what will happen. The facts will either finish Fox or save him, a novelty in these situations when reason tends to play little part.
There are justified and urgent questions being asked of the Coalition's policies, and more specifically in relation to Fox's bizarre conduct, but an inherently unstable political context highlights the needs for more stable government. Whatever happens to Fox, Cameron has set an example for ministerial continuity and his successors should follow it whether they lead a coalition or not.