In 1930 the former Lord Chief Justice, Lord Hewart, caused a scandal by writing a book accusing ministers of bypassing the Commons through statutory regulations having the force of law. It was called The New Despotism, and created the fuss it did because it was thought that such things ought not to be written by someone in Hewart's position, certainly not in readable form, most certainly not if they happened to be true. The result was a committee on ministers' powers. Everyone was happy.
Oddly enough, the House was a rather lively place during the war, despite - perhaps because of - its numerous secret sessions. But ministers continued to make regulations like billyo, as they continued to do merrily after the war had ended and, indeed, as they still do to this day.
The post-war period saw two additional and separate developments: the theory of prime ministerial government, and our membership of the European Union, as it is now called in a blatantly propagandist use of language, or the Common Market, as it was called in those days.
In the European Communites Act 1972 the House made Parliament's legislative powers subordinate to European law. Numerous politicians, including the prime minister, Sir (as he then wasn't) Edward Heath, denied they were doing anything of the kind. But they were, as was clear to anyone who could read. I told them, but they would not or, more likely, did not want to listen.
The theory of prime ministerial government cannot be marked so exactly, by an Act of Parliament or anything of that kind. It was in origin a child of the early 1960s. Its parents were John Kennedy, on account of the glamour he exuded as president of the United States, and Richard Crossman, on account of an introduction he wrote to the paperback edition of Walter Bagehot's The English Constitution.
Bagehot had drawn the distinction between the dignified part of the constitution, exemplified by the monarchy, and the efficient part, exemplified by the cabinet. The cabinet, Crossman wrote with typical bravura, had now joined the monarchy in the dignified part. The efficient part was made up of the prime minister and the cabinet committees, which might include civil servants and ministers who were not members of the cabinet.
It was the belated discovery of cabinet committees, then regarded as a matter of the utmost secrecy, which gave academic respectability to the theory of prime ministerial government. Indeed, the constitutional authority who wrote wonderingly of their existence resembled nothing so much as that other figure typical of the time, the middle-aged lady who had suddenly discovered the joys of sex.
Some prime ministers felt they had to live up to the theory: Harold Wilson, Margaret Thatcher, Tony Blair, as he was demonstrating in Belfast for most of last week. Others - James Callaghan and John Major - tried to revert to what they thought of as an older pattern. Edward Heath was an in-between sort of figure. At the end of his term he became the most presidential of them all, giving televised press conferences at Lancaster House on the French or United States model, at his right hand the head of the civil service, Sir William Armstrong (who was in due course to go mad, poor fellow, if he was not so already).
But from time to time something happens to dent the theories - for though often lumped together, they are really two quite separate theories - of parliamentary impotence and prime ministerial pre-eminence.
In 1940 the Commons did not make Winston Churchill prime minister. The beneficiary of their vote in the Norway debate might have been Lord Halifax. But they certainly made clear that Neville Chamberlain could no longer continue at No 10.
In 1969 the backbenchers told Harold Wilson and Barbara Castle that they were not prepared to support the proposals for trade union reform in the white paper In Place of Strife. They were withdrawn.
And in 1990 the Conservative backbenchers displaced Lady Thatcher in what was the most astonishing political event of modern times. For the theory had long maintained that no prime minister could be dislodged who possessed physical and mental health and an adequate parliamentary majority. Lady Thatcher fulfilled all three criteria except, possibly, the second one.
Certainly it is hard to say what precisely brought about her downfall - to stop the film, so to speak, and to be able to say: "There. That was the point at which she was a goner." As Francis Bacon wrote: "It were infinite to judge causes, or the causes of causes." One of the most revealing exchanges comes from Lord Parkinson's memoirs: "A colleague said: 'We are going to pin regicide on Heseltine.' The prime minister [Margaret Thatcher] looked puzzled for a moment, and then came the devastating riposte: 'Oh no, it wasn't Heseltine, it was the cabinet.'"
If it is any comfort to Mr Blair, I do not see any signs that his own cabinet is going to behave in this way, or that his backbenchers will revolt as Wilson's did in 1969. Wilson had a majority of 96 at the 1966 election, compared to Mr Blair's 177 last May. There are certain revolts which succeed - at least to the extent of inconveniencing the government of the day they succeed - because of the smallness of the government's majority. This was true in 1974-79 and in 1992-97. There are others which succeed because of the largeness of that majority.
The first kind of rebellion is built on alliance with the opposition, as it was over the Aircraft and Shipbuilding Industries Act 1977. The second kind is built on the old Labour principle of solidarity, of safety in numbers, of saying: "We love you dearly, comrade, but up with this we will not put." With the first kind of rebellion, the smaller the majority, the greater the chance of success; with the second kind, the larger the majority, the greater the chance of success likewise.
But since the great rebellion of 1969 and the smaller ones of 1974-79, there has been a qualitative change in the nature of Labour MPs. Even after nearly a year in which to acclimatise themselves, many of them still seem surprised to be where they are: not only surprised but some positively miserable.
My favourite story is of the new member who went to his regional whip and asked whether it was possible to resign. He had never expected this change in his circumstances to come about. As a result, he was out of pocket and his family life was suffering. The whip told him to behave himself; whereas the honest answer would have been that there was nothing to prevent him from applying for the Chiltern Hundreds at any moment he liked, which would have led to a troublesome by-election.
The preferred solution is to send batches of MPs of around 50 at a time back to their constituencies for a week of good works. A Westminster representative of the People's Party confessed recently that he had spent a pleasant few days working with his constituents in Amsterdam. How Tom Driberg would have loved to be a Labour MP today!