Mark Rothko's painting Black on Maroon has gone back on public display at London's Tate Modern gallery, 18 months after it was vandalised with graffiti.

The 1958 painting was defaced by Wlodzimierz Umaniec in October 2012. He was sent to prison as a result but has now apologised for his actions.

The Tate's conservators have spent 18 months repairing the painting.

Conservator Rachel Barker said: "It's definitely better than I could have hoped at the beginning of the project."