Sir Oliver Letwin was known as David Cameron’s Gandalf, the wise old wizard who was relied on to wave his wand over Whitehall’s Middle-earth in difficult moments. Combining an unworldly idealism with a ferocious attention to detail, he was the prime minister’s intellectual guru and backroom fixer.

His Cambridge PhD may have been on “Ethics, Emotions and the Unity of the Self” but it was his ability to crunch numbers and devour paperwork that made him invaluable to the Cameron administration.

The Old Etonian was trusted by Liberal Democrats as well as Tories in the coalition, and his courtesy and diligence won him the respect of civil servants. David Davis, now the Brexit secretary, once dismissed him as the Tories’ “Hampstead liberal” but other Conservatives