Sir Michael Palin is to undergo heart surgery.

The 'Monty Python' star has cancelled a planned book tour as he will have an operation in September to fix a ''leaky valve'' and has vowed to be ''better than normal'' when he's recovered from the procedure.

The 76-year-old broadcaster discovered there was a problem with his mitral valve - a small flap which prevents blood from flowing around the heart the wrong way - in 2014 but it only began to affect his health earlier this year.

He wrote on his website: ''Five years ago, a routine health check revealed a leaky mitral valve in my heart.

''Until the beginning of this year it had not affected my general level of fitness.

''Recently, though, I have felt my heart having to work harder and have been advised it's time to have the valve repaired.

''I shall be undergoing surgery in September and should be back to normal, or rather better than normal, within three months.''

Michael had been due to undergo a book tour to promote his 'North Korea Journal', a spin-off from his recent Channel 5 documentary, in October but this has now been cancelled while he recovers from the operation.

The 'A Fish Called Wanda' star - who turned 76 in May - previously admitted he doesn't feel his age because he looks after himself better now than he did was younger, although he conceded he is a ''little bit slower'' now than he used to be.

He said: ''I have realised that I have reached the age of 75 without feeling in any shape or form like someone of 75 - mentally, certainly.

''Physically, I think I'm a little bit slower perhaps than I used to be. But I'm still fairly fit. I'm probably fitter, and certainly look after myself better, than when I was in my mid-20s.''