I am writing a paper on various types of government structures and was trying to find out What are the mandatory positions in the cabinet of the United Kingdom. I know that every Prime minster has the choice of select his/her minsters and can add or subtract ministerial positions and even take up various positions if they choose to however I need to know those positions that will remain regardless what the Prime minster decides.
The Cabinet began as a sub-committee of the Privy Council. Initially it was a small group of senior advisers to the King. It is not defined by statute and so there is no position that is absolutely required, as a cabinet or a Prime Minister is not absolutely required by law. The Position of Prime Minister was originally satirical term, making fun of Robert Walpole, who then adopted the term.
The UK constitution is based not only on the law but on precedents and traditions. The Cabinet would, by tradition, require at least the Prime Minister, Chancellor of the Exchequer and Secretaries of State to be members of the Cabinet. Until the middle of the twentieth century this would be The Secretaries of State for Home affairs, Foreign affairs, War, The Colonies, and India.
This illustrates the flexibility of the system. There is no position that is fixed, up to and including the Prime Minister. Now of course there is no secretary of state for India, and the Colonies position has been subsumed into the Foreign office, and the Home Office has been split However Since the 1960s the head of each Government department has been converted to a Secretary of State.
Now all Secretaries of State would expect to be in the Cabinet, and since all Government departments are headed by a Secretary of State, the head of each department has to be in the cabinet. But there is also no definitive list of the departments of government. The system is entirely flexible.
There is an older system, that predates the office of Prime Minister, and would therefore in principle remain. The positions are known as the "Great offices of state" and are: Lord High Steward (vacant), Lord Chancellor, Lord High Treasurer (in commission to the Chancellor of the Exchequer), Lord President of the Council, Lord Privy Seal, Lord Great Chamberlain, Lord High Constable, Earl Marshal, Lord High Admiral. These positions are Now either vacant, or have become symbolic, with their tasks taken over by Ministers.