WHEN Mr Blair goes to see Her Majesty, she could refuse the dissolution of Parliament and tell him "Labour has a huge majority and if you can't form a Government I'm going to ask that nice Jack Straw to do so instead."

Technically she could, but she won't be inviting the Foreign Secretary and Blackburn MP, or even Chancellor Gordon Brown in for a chat over their future.

For the convention is that when the Prime Minister decides to call a General Election, the Queen dutifully agrees.

Indeed both Margaret Thatcher and Mr Blair have opted for four year rather than five year parliaments.

And recent history suggests they are very wise.

The last two Prime Ministers to go the distance Jim Callaghan and John Major have both lost heavily.

After Mr Blair has formally asked the Monarch to dissolve Parliament Lord Chancellor Lord Falconer puts an Order in Council to the Privy Council - the body of the great and good which traditionally advised the King or Queen before modern Parliamentary democracy evolved.

The Order is approved by the council and assented to by the Monarch dissolving Parliament under the Royal Prerogative.

There then follows four days of frantic activity as the Government attempt to get as much legislation through as possible before the final dissolution of Parliament.

The essential is to get a skeleton Finance Bill through the Commons and the Lords enacting as much of the budget as possible to ensure the Government gets "Supply" - enough money to keep going until the election campaign is over. And the new Government is in place for a proper Finance Bill and possibly a new Budget.

The party business managers will negotiate frantically through what are known as "the usual channels" with the speaker to get as much other legislation through as the opposition will allow.

This frantic horse trading "behind the Speaker's Chair" decides which Bills become law before Parliament finishes for the election and which don't.

Then the House of Commons is "Prorogued" - ending the current session and then dissolves for the election.

Government ministers remain ministers as Government continues despite the campaigning, but MPs are no longer MPs, just candidates.

The wedding of Prince Charles and Camilla Parker Bowles means that the business has to be wrapped up by Thursday night, giving an official election campaign of three and a half weeks - one of the shortest of recent times.

But several weeks of pre-campaigning make it seem longer, although not quite as long as the 1992 campaign when the political skirmishing amounted to almost a year before the official off.

Once upon a time Monarchs regularly refused dissolutions as they tried to cobble together the best available Government from the volatile politics of the time.

But following Sir Robert Walpole becoming the first "real Prime Minister" in the early 18th century this began to change.

The rise of the party political system - first "Whigs and Tories" and now Labour, Conservatives, Liberal Demcorats, Nationalists and others - underpinned the change.

The last time the Monarch refused the dissolution was in the early 19th century.

Under Queen Victoria the concept of the Constitutional Monarchy where the Sovereign took advice from the Prime Minister on all issues including dissolving Parliament grew up.