In the 1940s and 1950s there were several works saying that Parliament had lost power to what was called the executive. By this the learned authors did not mean principally the Cabinet but individual ministers operating through civil servants, who made rules which were unscrutinised by Parliament but nevertheless had the force of law. The war years and the immediate post-war years were, we should remember, the golden age of the civil service in this country.
The charge was not that the prime minister had become a president but, rather, that Parliament, by which was meant the House of Commons, had surrendered its powers to civil servants - and that at the same time the ordinary courts of law had been compelled to relinquish their powers to administrative tribunals controlled by Whitehall.
We had to wait until the early 1960s for the theory of parliamentary impotence to mesh with and reinforce the theory of presidential government. In 1962 the late John Mackintosh published his book on cabinet government. In it he revealed, with a wealth of contemporary and historical illustration, the existence of cabinet committees. They had, so Mackintosh informed us, assumed most of the functions formerly fulfilled by the Cabinet itself, and were effectively controlled by the prime minister of the day.
At this time Richard Crossman (who has also gone to a better place) was commissioned by Fontana books to compose a new introduction to their forthcoming edition of Walter Bagehot's English Constitution, first published in 1867. Bagehot had drawn a famous distinction between the dignified and the efficient parts of the constitution. Thus, according to him, the monarchy was dignified, the Cabinet efficient.
Crossman believed that any article - even quite a long article, such as his introduction was intended to be - should preferably contain one idea only. The more paradoxical, outrageous even, that idea was, the more arresting the article would be. (It is a journalistic policy that is followed today by Sir Peregrine Worsthorne.) Mackintosh gave Crossman his big idea. As the Cabinet had replaced the Crown, so the prime minister had now replaced the Cabinet, which joined the Crown as one of the dignified parts of the constitution. He developed these ideas in his Godkin lectures delivered in 1970 at Harvard University: or, rather, Mackintosh developed them, for though the words were spoken by Crossman, they had been written largely by Mackintosh.
Harold Wilson found the theory of presidential government entirely congenial. What could be more agreeable than to be described as a president? He had already implied a comparison between himself and J F Kennedy. Now, after 1966, he had a majority of nearly 100. It was at this time, not in 1964, that he began to talk about Labour as "the natural party of government". In 1970 he fought a presidential election against Edward Heath, who was widely believed to have no hope.
"Well, there's me," he said, "Wilson's the name, Harold Wilson, but everybody calls me Harold. Who do you want, me, or that other chap, forget his name now?"
"Thanks very much," the voters replied, "but if it's all the same to you we'll have the other chap."
Sir Edward briefly tried to cut a presidential dash with his televised press conferences from Lancaster House. These were said to have been modelled on the president's press conferences in the United States, but Sir Edward was thinking more of the example of Charles de Gaulle in France. At his side was Sir William Armstrong, the then head of the home civil service, who was referred to (much as Alastair Campbell is today) as "the deputy prime minister". He finally lost his reason, poor fellow, and had to be taken away.
Sir Edward, however, was not much of a presidential figure. Nor was Wilson in his third administration. Most of his passion was spent. He made a virtue of being merely chairman of the Cabinet. He would describe himself - for footballspeak is not an invention of the 1990s - as "a deep-lying central defender".
James Callaghan was perhaps the most dignified holder of the office of prime minister since 1945, someone with standards which he upheld. He never aspired to be presidential, though what we know suggests that he was both bossier and more bad- tempered than the impression which he liked to convey at the time. He would, however, make an excellent president of the new republic, if he managed to live long enough.
The 1970s was, significantly, a decade of small or non-existent parliamentary majorities. The theory of presidential government reached its peak (until today) in the late 1980s, when Margaret Thatcher had won three general elections. It was in 1988 that the magazine Samizdat was published, Charter 88 was founded, a human rights Bill became a progressive cause, and electoral reform was talked of once again. To Tony Blair's credit, he has already passed the Human Rights Act 1998, incorporating the European Convention into UK law and doing much else besides. For some reason it does not come into force until 2 October 2000, when it will, I predict, cause him and his colleagues a good deal of trouble.
But all this constitutional excitement of the late 1980s, which 10 years later has produced some though not a whole harvest of fruit, was brought about by fear and loathing of Lady Thatcher. She was, people thought, going to be there for ever, growing progressively madder by the month. And then she was gone, poof! in a puff of smoke, just like that, as the great Tommy Cooper used to say: except that on this occasion the trick worked. The theory of presidential government lay in several small pieces on the floor.
There was no attempt to revive it during John Major's lengthy period of office. How could there have been? But now, with Mr Blair at No 10, the pieces are being stuck together again. For such an attempt to succeed, at any rate in the eyes of easily impressed persons, three conditions must be fulfilled.
First, the prime minister must enjoy a large majority, as Mr Blair now does, and as previous exemplars of the theory - Macmillan, Wilson, Thatcher - did before him. Second, he must have a kitchen Cabinet, so that the broadsheet press can come out with over-excited articles about who enjoys "real power" or "has the prime minister's ear". Mr Blair can deliver on this front all right, with his Alastairs and Peters, his Anjis, Sallys and Sues. And third, above all, he must possess a "presidential" personality, of the kind Macmillan, Wilson and Thatcher all had at their peak, and as Mr Blair has today. The first two of these declined into shambling, slightly seedy figures.
There is a simple political point as well. Gordon Brown has enjoyed an excellent week, plaudits by the bucketful. Indeed, he has enjoyed an excellent two years. Not one Labour chancellor - not Snowden, Dalton, Callaghan or Healey - has survived this period at the beginning of a government without suffering a financial crisis. Mr Blair, by contrast, has not had such a good week. If Mr Blair is president, Mr Brown is chairman of the board or, if you prefer it, if Mr Blair is president, Mr Brown is the prime minister.