The grandfather of Britain’s new MI6 chief was a Nazi spy known as “the butcher”.

Second World War documents reveal Blaise Metreweli’s grandfather was Constantine Dobrowolski.

He defected from Russia’s Red Army to be the Nazi’s chief spy in Ukraine.

Ms Metreweli – known as “C” – is the first female boss of Britain’s Secret Intelligence Service in its 116-year history.

The Foreign Office – which speaks on behalf of MI6 was quick to distance the new “C” from her relative’s past.

A spokesperson said:

“She neither knew nor met her paternal grandfather”.

“Blaise’s ancestry is characterised by conflict and division and, as is the case for many with eastern European heritage, only partially understood.

“It is precisely this complex heritage which has contributed to her commitment to prevent conflict and protect the British public from modern threats from today’s hostile states, as the next chief of MI6.”

The Daily Mail discovered the family link after trawling through documents in an archive in Germany.

The paperwork showed Dobrowolski was know as “The Butcher” or “Agent No 30” by her Nazi handlers.

One “top secret” document is a 460-page alphabetical list of “foreign intelligence agents, traitors to the motherland, members of anti-Soviet organisations, punishers and other criminals subject to wanting”.

The archive suggests Dobrowolski stole from the bodies of Holocaust victims.

Also, he was allegedly involved in the murder of local Jews and laughed while watching the sexual assault of female prisoners.

Dobrowolski was on a most wanted list drawn up by the KGB.