A considerable amount of glitter came out of the TV set during ITV’s birthday celebrations. It was a telling reminder of how good the channel is at mounting mammoth razzmatazz. It was also a shameless if cheery exploitation of those twin concerns to which the network returns time and again: the need to see familiar faces soldiering ever onwards through an unfamiliar landscape, and the need to measure everyone’s lives and memories through television’s own self-compiled scrapbook.

The best tribute, the one that fluently combined both of these obsessions into a perfect whole and the one that landed a prestigious slot on the night of the 50th birthday itself, was also the one that for a long time didn’t look like making it onto ITV at all. Quite why Michael Apted’s 7 Up series found itself briefly ditched by the channel that reared it is baffling, and there are probably as many theories as there are conspiracists. Suffice to say mild confusion over whether 1998′s 42 Up was just a one-off deal with the Beeb only ceased a few months back, with the announcement that its follow-up would be amongst the centrepieces of ITV’s anniversary offerings.

This was great news for those who’d been scanning TV listings for weeks in search of clues as to 49 Up‘s very existence. Even more exciting was word that it would feature more contributors “than ever before”. This didn’t turn out to be quite the case, as of the original 14 participants only 12 turned up. But at least this was one more than last time and – given the number who used 49 Up to voice their bitter dislike for the entire project, one threatening to “bow out” there and then – a notable achievement in itself.

So what did the sometime future “shop steward and executive” allow Apted and his camera to discover? While mulling over the possible trajectories of the series a few years ago, OTT had suggested 49 Up would probably centre on “how the subjects are coping with their children growing up or in many cases having left home.” Not so; rather, it’s grandchildren who have emerged as the dominant focus for a significant number of the participants. This was unexpected. People becoming grandparents in their late 40s? You don’t really see that on television. And you don’t really hear people talking about it anywhere either.

Other assumptions were confounded. Contrary to small screen law that relatives must always be distant in terms of both genealogy and geography, a lot of the group had endeavoured, often at great cost, to keep their sprawling families close by. Two, Tony and Jackie, had sought to recreate the East End community spirit they talked of enjoying during their ostensibly tough upbringing by installing friends and relations to surround them in Spain and Scotland. In the face of what we’re told is an increasingly threatened world, all the subjects testified to being happier now than ever before. Some rejected Apted’s entire rationale. “Michael, I don’t think you ever expected me to turn out the way I have,” declared Jackie. “This is not an experience I’ve enjoyed in any way,” sighed Suzy. Most anticipated the grainy archive clips they knew would be cleverly intertwined with their new testimony could undermine their all-too-present words and thoughts. Some dared the viewer to revise their whole judgement about everything they’d seen up to this point in time.

All in all it was difficult not to come away from 49 Up feeling compelled to look a bit harder, a bit longer, at the world around you. Not necessarily an enticing prospect, of course, but one the series somehow ends up encouraging every time it rolls around. Intentional or not, Michael Apted prompts not just his subjects but also his viewers to think back to what they were doing seven years ago and to size themselves up accordingly. He then takes otherwise imperceptible changes and shifts in both the manners and foibles of British society, narrows them down to a dozen individuals, before blowing up the consequences into a state-of-the-nation essay.

This time, however, cause and analysis had dropped out of the equation. No mention was made of comparing the difference between the lifestyles pursued by those who came from lower class backgrounds with those from rarer stock. Indeed, nothing was said of how those who did have grandchildren came exclusively from less well-off origins, but who had at the same time travelled much further away from their roots than those who’d had the money and resources to journey around the globe from as early as 14.

Yet the complete absence of any such brooding examination was something you only noticed after the event. Its non-appearance during the programme itself wasn’t an issue. It wasn’t missed. In fact, quite remarkably – and utterly atypically – for a contemporary TV documentary, 49 Up didn’t seek to prove any points whatsoever. It didn’t tell us what to think. It didn’t even come to any conclusions. It just ended, minus any hyperbole, with a simple sequence cutting between pictures of the participants messing about in a playground at seven years old, and shots of them going about their business at 49. No grand summing up, no totalling of balance sheets, not even a promise of coming back again in another seven years. Here were your putative shop stewards and executives messing about on a Cornish beach, shopping for broccoli, playing amateur cricket and cycling through Cumbria. Now go figure.

Rather than feeling cheated, there was something of a sense of liberation at this, and of being free to reflect and surmise in your own time. Apted’s gentle but pointed interrogations ultimately turned 49 Up into a spiralling tapestry of voices – poignant, often angry, but always sincere. Moreover, the power of their words stayed in your head long after the programme had finished, thanks to the way the most plaintive of comments often came over sounding like the most sublime of maxims: “I still look up into the sky because I don’t know any better”; “We just live without our dreams”; “Who wants to be the richest corpse in the graveyard?”; “Life comes once and it’s quite short, and you have to appreciate what’s good in it.”

None of these carries much force written down, but when spoken by the assembled cast, and packaged as a footnote to their respective struggles and mixed fortunes, they sounded almost like poetry. On occasions, if you present even the most mundane of experiences in light of a lifetime of unexceptional circumstances, it ends up a universal truth. This may be insight or artifice, hackneyed or otherwise, but Michael Apted manages to rustle up a bounty of such clear-minded rhetoric every seven years. That he does so from a cast who seem forever ill disposed to him showing up on their doorsteps makes it all the more of a triumph.

Perhaps signing off with a promise to return again for 56 Up was tempting fate. After all, even Apted (now in his mid-60s) might not be around. Whatever happens, though, there will be some people there, just like this time, watching the schedules and waiting to reacquaint themselves with the same faces, the same moments from other people’s lives, and the same shared feelings of brutal appraisal and subdued, yet somehow uplifting, contemplation.