The guard took a pen to Anna Leporskaya’s avant-garde painting Three Figures on his first day working at the Boris Yeltsin Presidential Center in Yekaterinburg, the fourth-largest city in Russia.

The piece, which was painted between 1932 and 1934, is insured for 75 million roubles – around €880,000 or £740,000.

Anna Reshetkina, curator of the exhibition, said the guard’s “motives are still unknown but the administration believes it was some kind of a lapse in sanity”, The Guardian reports.

The work is now being restored at a cost of up to 250,000 roubles (around €3,000 or £2,500).