Edward Smith-Stanley

The UK's richest-ever prime minister, Edward Smith-Stanley, 14th Earl of Derby, was the head of government for three terms during the 1850s and 1860s, and goes down in history as the longest-serving leader of the Conservative Party. The aristocrat, who was a major landowner, had a fortune of some $9.3 million, which in today's money amounts to $1.3 billion (£1bn).