Russell Watson has revealed he almost backed out of the Rancid Rotisserie trial on I'm A Celebrity... Get Me Out Of Here! because the contraption reminded him of the MRI scanner used during his brain tumour treatment.
The classical music star, who has survived two pituitary tumours, said he became "panicky" upon being strapped to the rotating machine, which repeatedly dunked him into cold gunge as he attempted to correctly answer trivia questions.
Despite his claustrophobia, the 54-year-old, who was eliminated from the ITV show on Tuesday, managed to steel himself and complete the challenge.
"I would have liked to have done a couple more trials, but the one I did do was enough to last me a lifetime," he said.
"I was petrified as well because I am quite claustrophobic and it reminded me a little bit of the MRI scanner that I have been in, so I was a bit panicky.
"When they were strapping me in I was lying there thinking, 'I don't want to do this'.
"But I got to the point where I said, 'no, we are in here now so I might as well go for it'."
In 2005 Watson began having headaches and was diagnosed with a pituitary adenoma the size of two golf balls. He underwent a five-hour operation to have it removed.
Two years later he became incapacitated while recording his album Outside In and doctors found another growth, which was successfully removed.
The singer, who departed the show in a double eviction alongside soap star Jessica Plummer, said he had turned down the chance to appear on the programme six times because he feared he would not be able to keep up his complex medication regime.
"I didn't think it was something I would be able to do with my daily regime of drugs and steroids that I have to take after the tumour.
"One of the tablets is hydrocortisone - basically if I didn't take that for 48 hours I would be dead in a coma.
"But when I got there I started thinking, 'I can do this and I can get on with my life'."
Watson said he lost more than 9kg in the two weeks he spent in Gwrych Castle in Wales due to their restricted diet.
"I came out and I had lost nearly 20 pounds in two weeks," he said. "I put my pants on this morning because I thought I might smarten myself up and wear a nice suit today.
"I put my pants on and they literally fell down to the floor. I had to put two belts on just to hold my jeans up."