Bill Turnbull left red-faced after GMB airs his off-screen yoga session with weatherman Alex Beresford

GUEST host Bill Turnbull was left red-faced today after Good Morning Britain bosses secretly filmed his off-air yoga session with weatherman Alex Beresford.

The 65-year-old practised touching his toes while doing yoga squats during the advert break.

But when the programme returned, co-host Susanna Reid played out the clip of Bill bending over behind his desk as he worked on his flexibility.

Appearing not to have known he had been filmed, Bill said: "Nothing's private in the studio, nothing."

Explaining what was going on, Susanna said: "There was a very significant moment when Bill said 'can you put both hands on the floor and stretch your legs."

Charlotte Hawkins added: "As it turns out, Alex failed."

Bill replied: "It takes years to do. I thought I should be able to do it so I trained myself to do it."

The presenter was diagnosed with incurable prostate cancer three and a half years ago.

He told The Sun last week he experiences bouts of pain and “very dark days”, and continues to experiment with alternative therapies.

Explaining he uses yoga, garlic, ‘cannabis’ and an oxygen tent to battle the disease, Bill said: “I am now doing a lot of exercise which is structured, and supervised twice a week. I get on my exercise bike three times a week, 40 minutes on that, and do yoga every day, and some walking every day.

“Exercise is hugely important and yoga is very good for your mental health. I take probably too many different supplements — turmeric, berberine, a spoonful of black seed oil, which is like tar soaked in ­liquid, a sea fish oil and a teaspoon of my own honey.

“I take CBD, the legal form of cannabis, and the capsules are made from hemp. I also eat two cloves of raw garlic. It’s good for the blood but it’s not so good for making friends — and my wife has taken to kissing me in rather a different way now!”