Last night's viewing - Britain in a Day, BBC2

Britain in a Day – filmed by the plain people of Britain and assembled by Morgan Matthews – was, in the nature of its construction, a highly miscellaneous portrait of the nation. On Saturday 12 November last year, anyone who wanted to could film what they were up to that day and upload it to YouTube.

The result was enough footage to run unbroken for a month, from which Matthews, a documentarist with the stamina to match his fine eye, had edited together a midnight-to-midnight impression of who we are, both as a people and a species. By my calculation, this is a shooting ratio of something like 500-to-1 and the kind of challenge of distillation that might easily drive a lesser film-maker stark mad.A less polite word for a miscellany would be a ragbag, and when Britain in a Day began there were a few minutes when you feared that that was what you might be in for. The opening sequence had the groggy inconsequentiality of a home-run on a night bus after one too many drinks: there was Philip Glass on the headphones and a string of images challenging you to come up with a coherent narrative. Wake me up when we get to the depot, you thought, shortly before you saw a night-bus driver doing just that with a couple of limpet-like passengers.

But then the patterns and rhythms of the thing started to make themselves apparent. The first was a little clumsy – a straight cut from a breast-feeding mother to a farmer starting his pre-dawn milking and affably pointing out "the laziest cow I've got". From him, you went to a milkman and the early-morning shift at Radio Cumbria, and then into a montage of early risers: a boxer on a training run, hill-walkers and a rower, tugging his scull through the low mist on a river. You would become aware of a momentary theme – different ways of saying "good morning" for example – and then that would give way to some other echo. Matthews cut between an aging teddy boy and a punk getting their tonsures sorted for the day, and then to someone else impassively clipping his hair, as the sound of a family row leaked through the door.

Matthews was at pains to include pain, often touched in with a poignant economy. "These are my scars that I have collected over the years," said one woman, displaying a lattice of self-harming on the back of her hand. Another sat cheerfully with her pet rabbit and then dissolved into tears as she explained that it was a substitute for the child she couldn't have. Yet another shared her fear that she would never find a partner, her face crumpling at the thought. And in among the National Geographic stuff that any such enterprise will throw up – the pastimes and the scenery and the representative British eccentricities – Matthews had threaded two or three graver narratives to hold the film together. A father dying of a brain tumour prepared to attend his daughter's wedding in the hospice chapel and a young Scottish boy travelled to see his mother for the first time in five years, both of them wrenching evidence of how tightly the ties of family cling.

Not much was missing. Shopping seemed strangely absent and food had been reduced to a kind of percussive sound poem towards the end of the day. But we're now all well enough practised in the video confessional to cover pretty much everything else. Matthews was further helped by the chronological frame for the film, with its subliminal metaphor for the course of a life, from birth to death, sunrise to sunset. In the end, Britain in a Day was never going to be able to give anything other than the sketchiest impression of the nation. But it delivered a surprisingly comprehensive and moving account of what it is to be human.