Last Night's TV - Timeshift: All the Fun of the Fair, BBC4; DIY SOS:the Big Build, BBC1

Are dodgems the peak of civilisation? You know, the moment our social evolution stopped, and the ascent of man paused, in anticipation of the descent. That moment of classless solidarity that Marx and Jesus longed for, but Amy Winehouse knew could never happen. Are they?

I should think so, because there is no other invention whose achievement is to reduce adults of all ages and ethnicities to pure joy and irrepressible laughter. To look upon dodgems is to see a sea of smiling faces, of thrills and spills and all the fun of the fair. The nasty, brutish and short life prophesied for man is substituted for licensed but harmless violence, and the causes of war are exposed as futile distractions from the crucial business of bumping and bashing into one another with optimal force. The difficulty arises when the cars stop and the drivers have to be fed, naturally, but if all our lives could be spent exhibiting smiles – that is, on dodgems – we should be a happier species on a healthier planet.

It won't happen. But that we have this temporary version of utopia is owed to the magic of fairgrounds, as a beautifully composed Timeshift on BBC4 explained. Public spectacle is as old as civilisation, of course, but Britain pulled off a particularly magical version of it from the early days of Queen Victoria onwards.

As the late, tawdry, misanthropic, and irresistible News of the World might have put it: all human life was here. The girl in the bubble bath; the biggest rat in the world; the garrulous leprechaun; the shrink who could explain why men leave home. Showmen such as the legendary Tom Norman led the performances. They acted not only as front men – "talent" in their own right – but also as agents and proprietors on the pre-Victorian model.

As with so many BBC4 documentaries, our thrill as viewers came not just from the tour of yesteryear, with all its visual scintillation, but from the argument of the hour. Fascinating propositions and supporting evidence hit us constantly. Such as: there are three things fairground shows – which evolved in jerks because of the advent of the technology behind, say, rollercoasters – tended to boast. First, a bizarre story. Second, a sense of horror. Third, a touch of sex. We shall return to these presently.

Another powerful part of the argument was its contrarian tone. You've heard of the Elephant Man, Joseph Merrick, whose deformities led to him being the victim of appalling bullying and public humiliation, all of it directed, in fact, by Tom Norman, his agent. Except it didn't.

David Lynch's piercing 1980 film generated huge sympathy for Merrick, but only by falsifying history. The film introduced scenes in which Merrick was beaten by his employers, for which there is no evidence, exaggerated his exploitation, and even got his name wrong. They called him John instead of Joseph. Far from being a victim, the Elephant Man, whose exact condition scientists may have discovered only last week, was complicit in his own ennoblement. This historical corrective was refreshing.

Perhaps the most striking thing about fairgrounds was not picked up by the programme-makers. I have been thinking a lot in recent weeks about tabloid culture, and in particular whether we have a duty to mourn the aforementioned Sunday red-top. Those three properties of fairground shows – the bizarre, horror and sex – are basically the formula for tabloid journalism (in its modern form at least, and with some investigative nous thrown in). And fairgrounds did tend to cater for the audience red-tops cater for: the working classes, and the lower-middle class.

Towards the end of the show, the argument moved on to why fairgrounds might be in decline: natural atrophy, the rise of computer games and so on. An awful symmetry emerged, unnoticed by the producers. As the old working class ceases to exist, so fairgrounds have declined, and now the newspapers that embodied the same values are disappearing too. Talk about time shift: last night, BBC4's schedule wallahs were much more topical than they planned to be.

There was nothing topical about DIY SOS: the Big Build in Cirencester, except its Big Society impulse, or original about its formula: salvation for the needy. A family impoverished by the closure of Honda's local plant call in local volunteers to sort their house out. It was all laid on far too thick, of course. But the final group hug among uniformed locals was all very cheery, and it should be noted that on such occasions Nick Knowles is infinitely preferable to Laurence Llewelyn-Bowen.