Labour Party
Any Member of Parliament can be appointed Prime Minister of the United Kingdom. A person of Catholic faith may stand as a Member of Parliament, thus could become Prime Minister. However you cannot stand as a Member of Parliament if you are a member of the clergy.
The United Kingdom did not come into existence until 1707, so nobody was ruling it in 1245.
To be appointed as a Member of Parliament (and therefore eligible to stand as Prime Minister) you must be a British citizen, or a citizen of a Commonwealth country with indefinite leave to stay in the UK.
London is the capital city of the United Kingdom and Theresa May is Prime Minister of the United Kingdom. (June 2017)
In the United Kingdom, a cabinet minister is a member of the executive branch of a government who has been appointed to the cabinet, the group of leading policymakers of governmental departments who report to the prime minister.
In 2012 the Prime Minister of the United Kingdom was the Right Honourable David Cameron MP.
Yes
Tony Blair resigned as the Prime Minister of the United Kingdom on June 27, 2007. The current Prime Minister of the United Kingdom is David Cameron.
the Prime Minister, and the Queen
United Kingdom.
The United Kingdom
As "Prime Minister" or "Sir" in person. On letters, write the full title as "The Right Hon. Prime Minister of the United Kingdom PC MP" (PC=Privy Council, the most senior government officials MP=Member of Parliament) and begin the letter as "Dear Prime Minister"