Karl Marx's Grade I-listed memorial in Highgate Cemetery has been "mindlessly vandalised".

The marble plaque on the imposing sculpture's base has been attacked, seemingly with a hammer.

A cemetery spokesman said they did not know when it had happened, but believed it was within the last couple of days. No witnesses have come forward.

The marble was taken from the original 1880s grave which was moved about 50m (165ft) in 1956.

At the time, moving the bodies of Karl Marx and his wife to a more prominent spot in the cemetery was a controversial decision as it was during the height of the Cold War.

Ian Dungavell, chief executive of Friends of Highgate Cemetery Trust, said: "This is mindless vandalism, not political commentary.

"I'm really sad that it's happened in such an inarticulate way.

"You don't have to be a Marxist to think this is an important monument."

The sculpture is owned by the Marx Grave Trust and Mr Dungavell said the cemetery would work alongside the trust to help repair it.

This is not the first time the monument has been damaged. In 1970 a pipe bomb blew up part of the face, swastikas have been painted on it and emulsion paint has been thrown at it.

The Met Police said after making initial inquiries, officers have decided to close the investigation unless further information comes to light.