Paul Toole, 42, was left with a cigarette burn on his hand after feeling a searing pain while showing a group of visitors the execution chambers at Shepton Mallet Prison.
Paul, from Wells, Somerset, was telling the story of a Private Lee Davis, a former chain-smoking inmate who was executed for rape and murder, and refused to accept his fate before he was hanged.
"I had done a little research about the prison in the days leading up to the tour and it had been the very first time I had ever told this story to the visitors,” explained Paul.
"When I looked down at it later, it looked like a cigarette burn."