Alan Watkins: The question was fair. The Speaker was wrong. Mr Blair can look after himself

The Speaker could scarcely go back on his ruling three weeks later earlier The PM seemed embarrased by Mr Cameron's question

Some people do not mind the week between Christmas and the New Year: it enables them to collect their bearings, to have a rest. More of us, I suspect, find it a curiously unsettling period. A spell in purgatory, so the divines assure us, is even longer. The eight or nine months between the already announced departure of Mr Tony Blair and the accession of Mr Gordon Brown - though the precise date has yet to be fixed - is longer still, or so it must seem to us observers of the passing scene, not to mention those who practise the darker arts of Westminster.

So in 10 days' time, the Queen and her Consort will go down in a carriage to the House of Lords; a hereditary Dimbleby will perform, or perhaps it will be Mr Huw Edwards instead (for I have not troubled to inquire); that daft Cap of Maintenance, whose origins no one can properly explain, will put up another appearance, transported hither and yon; while Her Majesty will read out a prepared text, with that unique mixture of hers of bafflement and boredom; and then she will go away again. God save the Queen!

And what will it all mean? It will, I fear, mean very little, whether to Mr Blair or to Mr Brown. Of the two, Mr Blair is perhaps the more interested party, though the point is certainly arguable. He has, after all, his legacy to consider. But his legacy is buried in the sands of Mesopotamia. If you seek his monument, look about the ruins of Iraq.

It is a little late in the day to redeem his reputation with his Government's last programme. New initiatives, or old initiatives under new names, five-year plans, even 10-year plans: all may be blown away when Mr Brown becomes Prime Minister.

Last Wednesday Mr Speaker Martin ruled that the succession to Mr Blair was not a matter for Mr David Cameron to question but, rather, a matter for the Labour Party to decide for itself. The response from the television viewers, as vouchsafed by the BBC's Daily Politics programme, was that the Speaker was in error, and Mr Cameron was wholly justified in asking what he did ask.

He in effect repeated the question which he had asked of Mr Blair three weeks previously. This was about whether Mr Blair was prepared to endorse Mr Brown as his successor. And Mr Blair had not exactly floundered - for rarely if ever does he make an idiot of himself - but he seemed embarrassed; was at a loss. He certainly neglected to answer the question. This was understandable enough, not so much because he and Mr Brown have had their ups and downs (though they have) as because the subject was better left well alone, in the interests of all concerned.

Mr Cameron then secured another, separate victory, in the debased terms by which these encounters are judged. Alas, politicians being politicians, and the House being as it is, these are the only terms by which they can be judged. Mr Blair had attacked some bits of the Conservative programme, or it may have been the party's record, and he was called to order by the Speaker on the basis that the Prime Minister bore no responsibility for the Conservative Party or what it got up to.

This kind of intervention from the Chair is quite common - that the Government cannot question the Opposition because the Opposition is not in government - though successive Speakers have not always been consistent. In any case, an agile prime minister, such as Mr Blair is, can always turn round the question so as to compliment the Government instead. On this occasion, Mr Blair did his best, but it was still two up to Mr Cameron.

The accepted wisdom last week was that Mr Speaker had tried to restore the balance. Mr Cameron had won once; Mr Blair had been rebuked the second time around; so now the Chair was coming to the aid of the Prime Minister in time of trouble or, at any rate, of embarrassment. That was the predominant view of the Labour side. Mr Speaker Martin was being even-handed in his disapprobation.

There are two things that are wrong with this conclusion. One is that the Speaker had already allowed Mr Cameron's question about Mr Blair's successor. He could scarcely go back on his ruling - or, rather, make a different and opposite ruling - only three weeks later.

The other thing that is wrong is that the policy of the Opposition, for which the Prime Minister has no responsibility, is an utterly different matter from the identity of the next Prime Minister. Mr Speaker Martin says that this is for the Labour Party to decide. And so it is, to begin with.

This was what happened when James Callaghan succeeded Harold Wilson in 1976. Thirty years ago, it was the Parliamentary Labour Party that did the choosing. In 2007 a modified piece of machinery will be cranked up, of which the PLP forms only a part.

This does not mean that the House of Commons has no legitimate interest in the product of its mechanism. The Prime Minister is he or she who commands a majority of the House of Commons. He or she is usually the leader of the largest single party. Ramsay MacDonald had fewer seats than the Conservatives in 1924 and was brought down by the Conservatives and the Liberals, having lost the confidence of the house.

Extending the party franchise - for Labour since 1981, and for the Conservatives only since 2001 - has also created difficulties. For the party elections of Neil Kinnock, John Smith and Tony Blair there was in all three contests a unanimity among all parts of the electoral college. In Mr Iain Duncan Smith's election, however, the Conservative MPs had narrowly preferred Mr Kenneth Clarke. If Mr Duncan Smith had ever become Prime Minister, an unlikely event in any circumstances, he would have been imposed on the Commons, though no doubt the Conservatives would have become reconciled to this elevation when they realised on which side their bread was buttered.

No such difficulties arose with Mr Cameron. Nor will they with Mr Brown. As far as one can see, there is nothing but happy agreement; subject, of course, to the qualifications that are always made when Mr Brown's name comes up. Mr Alan Johnson is a phantom ship that has come and gone, while Dr John Reid has, it seems, made his peace with Mr Brown or has, at least, reached an accommodation with him.

Even so, the party is electing a leader, not a Prime Minister. Mr Cameron is perfectly entitled to question Mr Blair about who his successor will be, without any intervention on the Speaker's part. Mr Blair should be able to look after himself.