When Corden Met Barlow (BBC1) was the story of two men who came to know the fickleness of fame. One was the formerly chubby songwriter of Take That, stern X Factor judge and stubble pioneer Gary Barlow. The other was James Corden who was once hailed as the future of British comedy, until he outstayed his welcome and made a panned sketch show called Horne & Corden and terrible film called Lesbian Vampire Killers.
The reason James Corden was chosen to present this unexpectedly charming documentary is not, however, because he too understands what it is to be fêted, then ridiculed, then fêted again.
It's not even because, as Rob Brydon observed on The Guess List, he looks a bit like "a slovenly Gary Barlow".
It's because, believe it or not, Corden is a massive, massive fan of Gary Barlow's music.
It's an unusual favourite for a straight man in his mid-thirties to have, but after watching Corden's flawless mime to "Love Ain't Here Anymore", I can vouch for his fan credentials.
Corden was only too delighted to accompany his hero on a tour round the significant locations of Barlow's biography – the Cheshire working men's clubs, where Barlow first honed his performance skills (and moonwalk), the Manchester bar where Take That first met, and the country house where he hid away during the darkest days of his post-Take That depression.
There were a few nauseatingly obsequious observations from Corden ("Do you realise you're one of the few people on earth whose managed to get better looking as they got older?") but he also confronted Barlow with some genuinely unpleasant flashbacks.
Never mind wearing leather chaps and rolling around in jelly, real humiliation is being forced to watch a clip of Matt Lucas as "Fat Gary" presenting Robbie Williams with an award at the 2005 Brits.
"That was the worst bit of the whole thing," said an admirably candid Barlow. "It wasn't losing the record deal and it wasn't not singing for seven years... It was feeling like a dick."
Barlow's story, with its happy ending, is one of the best in pop music and there's no doubt that Corden has the hard-earned empathy to tease it out.
As much as the rise of the celeb-fronted documentary is a TV trend to be regretted, fame is one subject on which these celebrities are peculiarly well placed to talk.