Ageing rock stars have become a symbol of indignity in recent years. They're still going, they're still gurning, but the big question is: have they still got it?
Can they continue slithering into leather trousers when they really should be considering knee replacements? How are they still boarding tour buses when they are entitled to free travel?
What happens to the 'live fast, die young' doctrine when you reach the ripe old age at which an aspirin and an enema have to be added to the daily pharmacopeia?
Last night's Forever Young: How Rock 'n' Roll Grew Up, wasn't just about the birth of rock 'n' roll but the life cycle of the people at its helm. Naturally, The Who's My Generation ("I hope I die before I get old") provided the soundtrack.
Music trends have an inbuilt obsolescence, but rock 'n' roll defied the critics who branded it a passing fad. Likewise, many of its stars survived the orgies of excess for which the era was renowned.
The decision to grow old gracefully or disgracefully became the next challenge. Hearteningly, most chose the latter.
Iggy Pop, who at 63 is still a catatonic presence on stage, claimed he's only started to enjoy the fruits of his success in his old age, before reaming off the list of cliched status symbols he's achieved, from convertible cars to young women. "You know, so what if my knees hurt. I don't give a f**k," he blasted.
Lemmy, from Motorhead, was equally unrepentant.
"Live fast, keep going" is his variation on the old adage. His famous drug habit is still in working order, alongside a new-found compulsion for black hair dye.
Archive footage of Mick Jagger in an interview he recorded at the age of 38 came next.
"I think I can do this particularly physical show for another five years," he said. "After that it's going to look like Barry Manilow."
Cut to footage of old snake hips gyrating with the vigour of a man half his age almost 30 years on. His refusal to settle down came in for some criticism from other quarters. Joe Brown (who has appeared in pantomimes) considers it undignified. "How can you wear leather trousers when you're incontinent?" he asked.
How sad that a man who was once part of a movement that challenged convention, overcame critics and defeated censors could devolve into a small-minded ageist.
Forever Young wasn't just a fascinating look at the history and cultural impact of rock 'n' roll, but a challenge to the unjust expiry dates society tends to smack on those at its centre.
He triumphed at Wimbledon at the tender age of 17 and again at 18. He is a six-time Grand Slam singles champion and an Olympic gold medalist.
Yet, when Piers Morgan went head-to-head with Boris Becker in Life Stories, all I wanted to know was what exactly went on in that broom cupboard.
And I was guaranteed all the gory details with tabloid titan Morgan on the court. Like a true journalist, he warmed up his subject before broaching the big question (for the record, it wasn't in a broom cupboard, but a stairwell).
Keeping viewers entertained for one hour with just the dialogue of two people and a few talking heads is a tall order, but Morgan took to the task with flair and ease and led what was a consistently compelling interview.
Forever Young: How Rock 'n' Roll Grew Up
Piers Morgan's Life Stories HHHHI