We Brits used to be quirkily proud of our constitution. People say it's "unwritten" but it's truer to say it's scattered. Magna Carta; the Bill of Rights; the Parliament Act - it is to be found in many places. But it was never "entrenched" - meaning that any of it could be changed by a simple decision of Parliament. In three words the Constitution is "Parliament is sovereign". When you study it at university, they begin by telling you that "Parliament can make a man into a woman" and "Parliament can make it illegal to smoke on the streets of Paris".
This worked for a long time. But for a long time Parliament was a strong, vibrant institution comprised of independent minded people who did not defer to the executive branch of government. This was the Parliament of Cromwell, which did not hesitate to execute a king who sought too much power. Today's parliament is not much like that. The political parties have tamed it. And the political parties have tiny memberships - many of them fanatics and obsessives entirely uncharacteristic of the nation.
Today's Prime Ministers know that through the Whips - the party men and women who enforce discipline in the House of Commons - they decide which way the votes in Parliament go. Free votes are rare - party rebellions even rarer. The Whips' weapon is patronage. MPs know they will not advance if they disobey the party line. As a result, the men and women who take up that space once occupied by the great Parliamentarians of the past are are about as independent-minded as whipped curs.
The House of Lords is, sadly, an almost entirely ineffective second chamber. Lacking democratic credibility and packed with "Tony's cronies" it can be relied upon to collapse under pressure from the Government. If it ever does stand up for minority rights - as it creditably did over fox-hunting - the Parliament Act can be used to whip their Lordships into line.
If "Parliament is sovereign" and the members of Parliament do as the prime minister tells them, then we have not a Parliamentary Democracy but a Parliamentary dictatorship. If the dictator "loses it", anything is possible. Freedoms eight hundred years in the making, can be lost in days.