Vlad the vandal

Vladimir Umanets, the man who tagged a valuable Mark Rothko painting at the Tate Modern gallery in London this week, has declared: "I am not a vandal." We beg to differ.

It is difficult to find another word to describe the act of scrawling the words "Vladimir Umanets, a potential piece of Yellowism" on the canvas, in full view of astonished gallery visitors. Yellowism is, apparently, a movement that is "neither art, nor anti-art", and was founded in 2010 by Umanets and Marcin Lodyga.

The painting Umanets defaced, Black on Maroon 1958, was one of the Seagram murals, valued at tens of millions of pounds and given to the gallery by Rothko just before he committed suicide in 1970.

Umanets may believe himself when he says he has added value to the work. In an interview with The Guardian, he cited Marcel Duchamp, the early 20th century French artist who signed a urinal and put it on display.

At best, he is misguided. What he has really done is breached the bond that exists between artists and the galleries that exhibit their work, and more especially between public galleries and their audience.

To be able to see great works of art at close quarters is a privilege that not so long ago was reserved for the few. We may like what we see, or not; but we have no right to alter it. If Umanets thinks he can create great art, let him do so without trampling another's vision.