Last Night's TV: Britain's Fattest Man/Channel 4The Golden Age of Coach Travel/BBC4

Britain is in the grip of an obesity crisis," announced the voiceover at the beginning of Britain's Fattest Man. If, on the other hand, you're in the business of making freak-show documentaries about the morbidly overweight then things have never been better. You can find raw material on every street corner, as Rebecca Gilhooly's film demonstrated by providing a kind of hors-d'oeuvres montage of the grievously corpulent to underline her point. We saw a tubby woman tenderly cradling a box of Krispy Kremes, a lady as big as the sofa she sat on working her way through half-a-dozen sausages, and an almost perfectly spherical woman displacing startling amounts of water from her local swimming pool. And then Gilhooly hit us with the main course – Paul Mason from Ipswich, lying naked on his reinforced bed. For a moment, the mind scrambled to make sense of what you were looking at. It was alive... that much was clear... because it kept moving. But it looked less like a human being than a close-up on a kilo of uncooked sausages, or the strange globular assembly you get at the bottom of a cooling lava lamp.

Somewhere inside this catastrophe of flesh was Paul, who'd started comfort eating to cope with the stress of caring for his invalid mother and had crossed a point of no return. It took a team of carers four hours just to wash him every day, burrowing into the folds of his flesh to keep him infection free. "You lose those inhibitions, you know," said Paul, as two petite women wrestled with his belly folds to get into some of his more private crevices. But clearly he hadn't lost enough to make the situation painless. He was suicidally depressed and facing the possibility that even gastric bypass and stomach stapling might not be able to save him. Structural engineers had to be called in to ensure that the operating room floor would take the weight, and there was considerable uncertainty about how he would be transferred from home to hospital. "I did wonder about a Chinook," said his surgeon.

Paul had become a welfare scandal – the £100,000 it cost annually to keep him going having attracted tabloid indignation. In truth, it struck you that he was a victim of the welfare state as much as its beneficiary. In a harsher age he simply wouldn't have been able to afford to get this bad. But now – having at some point been diagnosed as ill rather than feckless – his disease was effectively being aggravated by the systems set up to care for him. He could barely lift a finger for himself, but then he didn't need to anymore. "I cook him whatever he likes," said one of his carers. "It's all good food." Not in his case, you thought, as you watched him ploughing into his dinner. Sympathy for him flickered and guttered – strong when he talked of the despair he felt at his loneliness and self-disgust, weakening considerably when he moaned about feeling "abandoned" after the funding for his care was cut back.

After which you got surgery of a different kind, literally stomach turning in the case of the initial intervention, which left him with just an egg-sized pouch into which to feed future calories, but grisliest when he returned to have one of his thigh dewlaps removed – 10 kilograms of flab that puddled in the bottom of the waste bin after his surgeon had heaved it off the table. By the end of the film he still couldn't stand on his own two feet, but he did at least appear to be travelling in that direction on his mobility scooter. Documentary-makers anxious to break into this burgeoning genre should not be too fretful though. Somebody will soon come along to replace him.

Britain's Fattest Man was, I guess, water-cooler television, just the kind of thing to provoke fascinated "Did you see?" inquiries the following day. Debbie Martin's film The Golden Age of Coach Travel was the very antithesis of water-cooler television, unless the cooler in question happens to be located in a road transport museum, where an excited crowd might well convene to rhapsodise about toast-rack charabancs or the glories of the Yelloway livery. It was a lovely programme though, marinaded in the guileless pleasure of the enthusiast, across whose discourse the shadow of self-doubt never falls. It simply never occurs to them that anyone might be bored by their passion and there's a charm in that alone.

The Golden Age, if you're curious, seemed to run from just after the First World War (when demobbed soldiers bought surplus army vehicles to transform into charabancs) to somewhere in the early Sixties, when the rise of private motoring finally put an end to mass coach travel. In between there was social history (the Holiday with Pay Act of 1937 increased the demand for coach services), intriguing detail (some drivers would chalk a roulette wheel onto one tyre and run a modest sweepstake on which number would come up at the next stop) and great waves of misty-eyed recollection. They were called coach parties for very good reasons, it seems, the conviviality of the passengers and the unaccustomed sense of frolic that often accompanied early outings leading to a kind of rolling bacchanal, with the driver as a jovial compere. I assume there must have been some passengers who found it tiresome to spend two days travelling from Rochdale to Torquay but you didn't hear from them here, and the film was none the worse for that.