LONDON -- The British Constitution has long been widely admired, if not always understood.

The fact that it was unwritten, and therefore capable of endless adaptation without too much fuss, was seen as its great strength. The central idea, emerging out of the constitutional struggles of the 17th and 18th centuries, was that Parliament, in the form of the elected House of Commons, was supreme, and that the executive, although nominally governing in the name of the Crown, was subservient to Parliament, where all power lay.

That was the theory. In practice things have turned out very differently. It is not Parliament, but the political party with the largest majority in Parliament that is supreme. The party machine rules all. It controls the Commons, not the other way round. It can, of course, be turned out at a general election by losing its majority. But between elections the party and its leaders are all-powerful -- described, correctly, as an elective dictatorship that combines the powers of both a president and prime minister and can in practice do anything it pleases.