When was the Derby won by the reigning monarch, and when by the incumbent prime minister? asked Ian Cooper
The only Derby won by the reigning British monarch was back in 1909, when Minoru followed up his victory in the 2000 Guineas with success at Epsom.
Minoru was owned by King Edward VII - who, when Prince of Wales, had also won with Persimmon (1896) and Diamond Jubilee (1900).
Two years before Persimmon's success, the Derby was won by Ladas, whose owner - the Earl of Rosebery - was the British Prime Minister at the time.
Rosebery won the Derby again in 1895, with Sir Visto, shortly before a vote of no-confidence in the House of Commons led to an election, which his Liberal party lost.