Shortly after news that the prices for Mark Rothko paintings had rocketed the police are investigating the defacement of a work by the 20th century abstract artist at the Tate Modern in London.

The work, ‘Black on Maroon’ (1958), was gifted to the Tate by the artist and hung in a room with several other works painted by Rothko, one of America’s most important artists. The museum said in a statement: “Tate can confirm that at 15:25 this afternoon there was an incident at Tate Modern in which a visitor defaced one of Rothko’s Seagram murals by applying a small area of black paint with a brush to the painting.”

An eyewitness, Tim Wright, wrote on twitter, “This guy calmly walked up, took out a marker pen and tagged it. Surreal.” He later uploaded a photo which showed the dripping black tag. It appeared to read “Vladimir Umanents, A Potential Piece of Yellowism.”

According to an online manifesto, Yellowism is a movement run by two people named Vladimir Umanets and Marcin Lodyga. The manifesto announces that “Yellowism is not art or anti-art”, and that “Every piece of Yellowism is only about yellow and nothing more.” It is believed to be inspired by the early twentieth century, anarchic art movement Dada.