The 77-year-old former Goon faces a punishing series of radiotherapy sessions over Christmas.

Sir Harry, nowadays best known for presenting Songs of Praise on BBC One, was told six months ago that he had a malignant tumour on his prostate gland.

He kept the news from all but a close circle of friends and continued to work while receiving treatment for prostate cancer, which killed his friend and fellow Goon Michael Bentine two years ago.

Michael Bentine succumbed to prostate cancer in 1996

In an exclusive interview with the Daily Mail, Sir Harry said more men should be alerted to the dangers of prostate cancer.

About 300 Britons develop the disease each week and 9,000 men die as a result each year in England and Wales.

Around 80% of men older than 80 develop prostate cancer but most will die first of another illness because it takes a long time to develop.

'Lot of prayers'

A committed Christian, he said: "I am fighting this from the inside. I have done a lot of praying, and I am surrounded by my wonderful family and some great friends."

Sir Harry said he was going on holiday abroad with his wife of 51 years, Myra, before embarking on the "punishing" radiotherapy sessions.

"But I'm a tough old so-and-so and I'm not feeling too bad," he said.

Sir Harry even managed to laugh in the face of adversity, saying: "I'm planning a long life, unless a number nine bus tells me different."

He is having hormone treatment in a bid to reduce the size of the tumour but managed to film the Christmas edition of Songs of Praise last week.

"I have got to be positive about it. There is no point in getting down and brooding about it. Once you know what you have got then the mystery has gone and you can get on with it," he told the Mail.

In 1982 Sir Harry suffered a perforated colon and the following year he collapsed at a concert in the Sydney Opera House and was diagnosed as diabetic.