Having a pacemaker fitted has not stopped veteran wildlife broadcaster Sir David Attenborough climbing trees, he has revealed.
Sir David, 87, who has also had knee replacement surgery, said his insurers insisted on him having the device fitted.
"I had to go to Australia and the insurance said they wouldn't insure me to go on a long flight unless I had something to monitor my heart to make sure it didn't do funny things," he said.
"So they give you this thing, it's called a pacemaker.
"And all it does, if your heart suddenly decides it's going to skip a beat or something, it kicks in. And if it doesn't, it doesn't.
"And I don't think it has."
But, appearing on tomorrow night's The Jonathan Ross Show Christmas Special on ITV1, he said the operation had not held him back.
"I've just come back from Qatar and before that was in Rome and I'm just off to Borneo," he explained. "I only do it because it's fun.
"I'm not as good at climbing trees as I was, but I've been up in a tree recently."
On the same show, John Bishop described how depression led to him getting into comedy. The Liverpudlian comedian said he had split up with his wife and was hitting the bottle on Monday mornings after seeing his children at weekends.
He said: "You're thinking the world's great for everyone except you... it was becoming a regular thing and then what happened after about four or five weeks, I thought, I've got to make myself do something on a Monday and that's what made me go to a comedy club for the first time.
"To not be in the house... and that obviously started the chain of events which lead to this."
Also during the show, chef Jamie Oliver revealed how actor Robert De Niro once sent back pasta in one of his restaurants.
"He came in and he ordered off menu, he ordered spaghetti arrabiata," he said. "Arrabiata means angry.
"And I believe I have a very good recipe. But he sent it back because he said it weren't hot enough.
"And it was hot.
"So that boy likes hot stuff."
