Prince William of Gloucester (b. 1941)
Prince William of Gloucester (William Henry Andrew Frederick; 18 December 1941 – 28 August 1972) was a grandson of King George V and paternal cousin of Queen Elizabeth II. At the time of his birth he was fourth in line to the throne, and ninth in line at the time of his death.

A Cambridge and Stanford graduate, he joined the Foreign and Commonwealth Office, serving in Lagos and Tokyo, before returning to take over royal duties. He led an active life, flying Piper aircraft, trekking through the Sahara, and even ballooning.He remains the most recent descendant of George III to be diagnosed with porphyria, probably hereditary, which is widely believed to be the illness that most likely caused George III's mental breakdown.Prince William died in 1972, aged 30, in an air crash while piloting his plane in a competition.