It was famously pointed out on the BBC TV comedy panel show QI that the office of Prime Minister didn't officially exist in the UK before the 20th century.
In 1721, following the collapse of the South Sea Company, King George I called upon Robert Walpole to handle the emergency, appointing him as First Lord of the Treasury, Chancellor of the Exchequer, and Leader of the House of Commons.
Walpole, the Member of Parliament for King's Lynn, was a Whig from the gentry class. His father had been MP for Castle Rising, which (like King's Lynn) was a pocket borough in Norfolk. Over the next 21 years, Walpole skilfully stabilised the nation's finances, maintained peace and prosperity, and secured the Hanoverian succession. He demonstrated how the sovereign's chief minister could be the actual head of government, and he established the dominance of the Commons over the Lords. But he insisted that he was nothing more than the King's servant. In 1742, when a political opponent (in the speech that would ultimately lead to Walpole's downfall) attempted to dismiss any claim that he might have to the title of Prime Minister, Walpole "unequivocally denied" making any such claim.
Wikipedia quotes several of Walpole's successors denying the existence of the title, until well into the 19th century.
The first official recognition of the title came in 1878, when Benjamin Disraeli signed the Treaty of Berlin as "First Lord of the Treasury and Prime Minister of her Britannic Majesty". (The Treaty of Berlin followed the conclusion of the Russo–Turkish war; it effectively established Bulgaria as an independent state, in order to prevent a Russian client state in the Balkans.) But there was still no legal authority behind the office; as late as 1904, Arthur Balfour said in a speech: "The Prime Minister has no salary as Prime Minister. He has no statutory duties as Prime Minister, his name occurs in no Acts of Parliament, and ... he has no place which is recognised by the laws of his country. This is a strange paradox."
In 1905 however, the position was given official recognition when the Prime Minister was named in the order of precedence, outranked (among non–royals) only by the Archbishops of Canterbury and York, the Moderator of the Church of Scotland, and the Lord Chancellor. QI dated the official creation of the post to five days after the election of Henry Campbell–Bannerman – i.e. 10 December 1905. Campbell–Bannerman, according to QI, was the first Prime Minister of the United Kingdom.
If asked in a quiz, however, who was the first Prime Minister, you would be best advised to answer "Walpole". For this we have the support of no less an authority than the Prime Minister's Office itself.
© Haydn Thompson 2017