An 800-year-old sandstone coffin was damaged when a family of visitors put a child inside it so they could take a souvenir photo.
Security camera footage from the Prittlewell Priory museum on August 4 showed the family lifting a child over a barrier so that he could reach the sarcophagus. Part of the coffin, which was already in three pieces, fell from its stand and a chunk broke off.
The visitors then sneaked away from the museum, in Southend-on-Sea, Essex, without telling anyone about the damage they had caused.
The coffin was found in the grounds of the priory in 1921 and had a skeleton inside, which is believed to have been that of a monk.