A group of first aid trainees thought their instructor was role-playing during a class on how to perform life-saving CPR as he had a heart attack during a lecture.
David Knowles, 77, began to lose consciousness as he told his students how to resuscitate people at his local church in Exeter.
Some of the group thought Mr Knowles was giving a demonstration as he lay on the floor feeling faint and unwell.
He would have died at the scene if nobody was there to help him.
Mr Knowles said: “I’m told I came to, briefly, and was talking to the paramedics about my condition, but the next thing I remember is waking up in hospital, two and a half weeks later.”
They managed to save the Trainer’s life after he told them what to do just before he passed out.