Last night's viewing: When I Get Older, BBC1 River Cottage: Three Go Mad, Channel 4

Is there any phrase more depressing – in the context of television at least – than "It's Day One"? Just three short words and yet enough to tell you that what you're about to watch has already succumbed to formatitis, a condition in which the narrative architecture of a programme becomes inflamed and begins to obscure its subject matter. The suspicion that When I Get Older had gone down with a dose was quickly confirmed by two other details: it involved celebrities condescending to live with civilians and it began with the strenuous creation of ersatz jeopardy. "I feel a bit nervous... a bit apprehensive," Gloria Hunniford said obligingly as she was driven to the Lancashire terraced house in which she was going to spend four days with a local pensioner. And then, just in case you hadn't got the point, the narration waded in too. "This may turn out to be one of John's toughest assignments yet," we were told as John Simpson made his way to his billet. No it won't, you bloody idiots. He's had colleagues killed alongside him.

Let's be fair and concede one thing. All four celebrities involved in this consciousness-raising exercise about the tribulations of aging were genuinely being a little bit brave. They were, effectively, coming out as old, within a culture that hasn't always shown itself very understanding about that temporal alignment. Broadcasters have lost their jobs for being old, let's remember. And quite apart from the professional hazard there was a risk to personal vanity too. You might not think about John Simpson or Gloria Hunniford's age when they're at work doing their day job. But if they're on screen as "famous pensioners", you look a little more closely at what age has done to them.

Their task – another symptom of formatitis – was to play celebrity godmother to four representatively beleaguered pensioners, struggling with poverty, isolation, grief and the pressures of caring for a disabled partner. And, when you could get a glimpse of these stories past the scaffolding, they were touching and instructive. "I want him back, I want him being the horrible, frustrating thing he used to be," said Pat about her bedridden husband, Malcolm, who was now frustrating in a way that Pat didn't feel entitled to complain about. Phillip was still mourning his wife of 68 years, unable to sing their favourite songs without choking up halfway through. And Ivy was so short of money that she was left with just £3.24 a day to live on.

With at least three of the cases, the attention (and a bit of advice and nudging) did make a real difference. A wand of sorts was waved. But John Simpson gave up on the apparently thankless task of reconciling Peggy with her local villagers, settling instead for humanising her a little by filling in the details of her own loveless childhood. When he persuaded her to take a trip out for the day the only place she wanted to go was her father's grave, the one person in her family who'd shown her affection. And then Simpson himself, in the teeth of his own resolution not to, choked up at the thought of how old he would be when his six-year-old son turns 16, just as Gloria Hunniford had wept remembering her dead daughter. The vulnerability of celebrities wasn't really what this film was meant to be about, but in its way it made a point about the vulnerability of all of us, to the regrets and exposures of age.

More celebrities in River Cottage: Three Go Mad and even more fake hazard, as Hugh Fearnley-Whittingstall introduced three actors to country living and country cooking. "Will Felicity wow the crowd with her nettle soup? Or be stung by the reviews?" "Can Keeley's stew bowl over her new showbiz pals?" "Will it be curtains for Philip and his mackerel?" Oh. Which will it be? I can hardly move for the tension.