'I was told I should be using a zimmer frame'

It was an agonising TV moment - but not as painful to the viewer as it was to Roger Cook, when a collapsing chair during Sunday night's opening episode of Hell's Kitchen swiftly put paid to his spell as one of Gordon Ramsay's "pupils" training to be a chef.

As the chair broke, Roger crashed to the ground with his vulnerable left knee taking the brunt. "I'm terribly disappointed," he says.

"Everything was going so well after the fifth operation on my knee - which is basically a replacement. Although I was still on painkillers, my 'new' knee was working well.

"The replacement was very sturdy but now it's all black and blue. I've been told that manipulation of the replacement under anaesthetic might work, or I might have to have it operated on again. But I'm back on crutches and back to square one."

"Square one" was just after that miserable fifth operation on Cook's knee. "This young doctor turned to me and said, 'Perhaps you'd find a Zimmer frame more suitable, Mr Cook.'

Okay, I may have just had an artificial knee fitted, but what a bloody cheek! There was no way I was going to use a Zimmer frame. What an intimation of age!"

For a man who spent most of his 30-year career chasing conmen and criminals, vaulting fences and leaping from surveillance vans to bring them to justice, the thought of such an undignified fate at the tender age of 61 was too much to bear.

But Cook was confident that this final operation on his knee had been successful and despite this latest set-back, he is still optimistic. "My orthopaedic surgeon inserted something called the 'Oxford Knee'. Although I call it my 'tin knee', it's actually an incredible invention.

"It's a replacement hinge-joint, made of hitech lightweight metal and plastic. The small device stands behind the kneecap, and the cylindrical surface of the artificial 'bone' fits into the groove of another to form the joint, which either bends or straightens a leg."

Cook only resorted to the extra surgery because his knee was so badly damaged that walking would have been impossible.

"I never thought this is how I'd end up the moment I hit my sixties. Most of us expect to have to deal with dodgy hearts or weight problems when we hit middle age, but it seems an increasing number of us are going to end up like me, hobbling around with iffy knees."

His injury came about after years of strenuous sport, particularly rugby. Cook was in the scrum when he felt his knee tear. Surgeons repaired the cartilage, only for it to keep on tearing over the years, until it wore out.

"Younger people should be aware of the damage that can be caused to knees and how serious it can be," Cook continues.

"They need to know that if they get injured, they shouldn't just carry on; they must see a doctor and get the right treatment. By ignoring it, they are very likely to be looking at that Zimmer frame in the years to come."