On the evening of 20 August 1940, a man known as Frank Jacson called at a large house in the suburbs of Mexico City, and asked to see the ‘Old Man’ – as everyone called its celebrated resident, Leon Trotsky.

A few minutes later, the tip of the axe was buried more than two inches into Trotsky’s skull, becoming arguably the world’s most infamous murder weapon. 

The axe was fleetingly displayed at a police press conference, but then disappeared for more than six decades. 

Next year, however, the bloodstained relic will go on public display at Washington’s International Spy Museum, which will reopen in a new building to accommodate thousands of other artefacts that have emerged from the shadows.