Police are hunting for a vandal who walked into the Tate Modern art gallery and defaced a valuable painting by Mark Rothko.
The visitor daubed black paint on the mural piece during a visit to the popular landmark yesterday afternoon, a spokeswoman for the gallery said.
The art gallery said it does not have a price for the defaced piece, but paintings by the Russian-born artist often fetch tens of millions of pounds.
Earlier this year, Rothko's Orange, red, yellow was sold for £53.8 million - the highest price ever paid for a piece of post-war art at auction in New York.
Scotland Yard confirmed it had launched an investigation into the matter and is yet to make any arrests.
The force said it was looking for a white male in his late 20s.