Gregor Formanek is accused of participating in the murder of 3,300 people when he was a guard at the Sachsenhausen concentration camp, near Berlin, between July 1943 and February 1945.

Proceedings against him were suspended earlier this year due to a “permanent inability to stand trial”. That decision has been overruled.

A document drawn up by the East German secret police, the Stasi, states that Mr Formanek, who was a teenager at the time, “continually killed prisoners”.

Sachsenhausen was used to imprison Jews as well as Soviet soldiers and others — tens of thousands of people were murdered there.