British cabinets usually consist of about 22 politicians, mostly elected Members of Parliament, who head a government department, such as health or transport.

There are also two or three ministers from the House of Lords, including the head of the legal profession, the Lord Chancellor.

The full Cabinet meets once a week, every Thursday morning, to take its main decisions.

But it also is broken up into a large number of regular committees (such as economic policy or defence) and ad hoc committees, which meet from time to time on special issues and bring in outsiders to help and advise.

Ministers are serviced by a Cabinet Office and senior civil servants often attend meetings.

The power of patronage

All members of the Cabinet are personally appointed by the prime minister.

This gives him great powers of patronage - both to sack under-performers, and to bring on "successes", good communicators and rising stars from the the other 80 or so members of the government in junior posts and the whips' office.

Reshuffles usually occur in the summer, just before the recess, to give ministers a few months to read themselves through the break.

'Butchering' the Cabinet

Some prime ministers enjoyed reshuffling their pack, others hated it.

It has been said that a good prime minister "has to be a good butcher".

Harold Macmillan in the famous "Night of the Long Knives" once sacked six cabinet ministers in a day.

Cabinet development

Cabinets are the modern development of the small group of advisers who in the 17th and 18th century surrounded the King or Queen.

Queen Elizabeth I relied heavily on Lord Burleigh. George I, who spoke no English, and his successor George II, relied on Sir Robert Walpole.

Walpole was technically First Lord of the Treasury and he became, over a period of 21 years in Downing Street the first prime miniister.

Modern Cabinet government further developed in the 19th century under Palmerston, Disraeli and Gladstone.

In two World Wars, Lloyd George and later Churchill ran affairs through a small War Cabinet, leaving domestic affairs to departmental ministers.

Executive and Legislature

Cabinets can take most decisions affecting British life - they can declare war, make treaties, raise taxes, propose laws - provided the ruling party can maintain its majority in the Commons.

Only if the majority slides through loss of seats at byelections , as happened to James Callaghan and John Major - can ruling become difficult.

A government without a parliamentary majority sooner or later has to resign, or will be overthrown.

But all cabinet decisions need the sanction of both Commons and Lords - put another way, the Executive is subject to the Legislature.

Unpopular bills can be held up, and even thrown out, if blocked by groups of MPs or peers.

Evolutionary system

The system of Cabinet government in Britain has evolved but never been threatened.

MPs have recognised that in time of war, and emergencies, such as the Falkland War, power has to be concentrated in the hands of a small inner cabinet to take quick executive decisions.

The Labour government was accused in 1976 by the former Tory Lord Chancellor, Lord Hailsham, of running an "elective dictatorship".

By this, he meant forcing through nationalisation and other measures against the will of the majority.

But that in turn was used by Labour against Mrs Thatcher, who they felt was overriding her own ministers, on such matters as the poll tax, to get her way.

But she, in turn , was overthrown by her own Cabinet.

And British governments rarely have the support of a majority of voters.

When a government has a very large majority - as Mr Blair's does now - it is fairly easy to get bills through the Commons

But this puts a greater onus on the House of Lords - where the government has suffered over 30 defeats this session.

The composition of the House of Lords is currently under threat.

Role of the monarch

In theory the Cabinet consists of the Queen's ministers and they act in her name.

All bills before becoming law have the words "La Reine Le Veult" pronounced over them .

Not since Queen Anne has a sovereign refused to approve a bill.

But nowadays, in practice, the Queen's powers are restricted to advising and warning the prime minister.

This is an important role when she has 45 years experience of prime ministers, politics and overseas personalities, compared to Mr Blair's single year in the job.

Ministers kiss hands on appointment, and receive their seals of office from her; and are mostly made members of her Privy Council.

This used to be a group of senior advisers to the sovereign, but now is more of a recognition of status, allowing MPs to put "Right Honourable" before their name.

She is the fount of honour, and has the last word on Honours, postage stamps, protocol, state visits, and a number of formal matters; but she is above politics.

She has dealt with party leaders and governments of all parties, and has subtly adapted to the changing scene, including making herself liable to income tax.

But the true power in Britain still rests with the British Cabinet - with the support of the ruling party, and its Parliamentary majority.