A security guard (R) looks on as employees pose with a work of art by Russian born US artist Mark Rothko entitled 'Black on Maroon' 1958, during a photocall at the Tate Modern in London, on May 13, 2014. The painting has gone back on display at the Tate Modern after 18 months of restoration following an act of vandalism in October 2012. Wlodzimierz Umaniec was jailed for 2 years in December 2012 for defacing the painting. AFP PHOTO/BEN STANSALL.

A woman poses for pictures with a work of art (R) by Russian born US artist Mark Rothko entitled 'Black on Maroon' 1958, during a photocall at the Tate Modern in London, on May 13, 2014. The painting has gone back on display at the Tate Modern after 18 months of restoration following an act of vandalism in October 2012. Wlodzimierz Umaniec was jailed for 2 years in December 2012 for defacing the painting. AFP PHOTO/BEN STANSALL.