Even now, when schoolchildren forego their playtime Caramacs so that they can put the 27p towards their pension funds, there are still some things you're not likely to do before you're in your mid-twenties: get divorced, for example, or tell your friends that you're "really getting into jazz at the moment". Another thing you're not likely to do is attend a reunion, and last weekend I found out why.

I was collecting my MA from Cambridge - the University maintains a mysterious tradition whereby your Bachelor of Arts degree is bumped up to a Master of Arts after three and a half years, even though you haven't done a stroke of work in the meantime (not that everybody did a stroke of work in the first place). The college gets a small fee out of the deal, and the graduands get to return to their alma mater, hire a black gown for what was once a term's worth of food money, and meet up with their old pals. Current students get the chance to snigger at these sad, past-it interlopers.

Once I'd taken the train from London to Cambridge (stopping off at Audley End, Stansted Mountfitchet, and all the other towns that have deliberately picked stupid names, just to make the interruption of the journey that bit more annoying), my first shock was seeing how much buildings can change in a short space of time. The historic Sixties architecture of my college (most famous alumnus: Norman Lamont) had been tampered with. Trees had been planted, whole new wings had been built. My time there - all of four years ago - seemed like ancient history, before the first Oasis single, before the first episode of Friends was broadcast. After all this time, what on earth could my former colleagues be up to?

One lunch "in hall" later, and the question was answered. They are systems analysts or accountants. One or two people have thrown caution to the wind and become lawyers, but the rest are systems analysts or accountants. Now, no offence to all those who practise these noble arts, but when you tell someone that you are a systems analyst or an accountant, what are they supposed to say? What conversation is supposed to ensue? It was a problem I wrestled with throughout the course of the day.

After lunch, we crowded into a conference room, where the college praelector explained what we should do at the graduation ceremony. It would, in short, be exactly the same as the one four years ago, but that wasn't the only thing which worked its deja voodoo. Everyone was grouped in - and out of - the same cliques as they were the last time round; the same people interrupted the briefing with the same smart comments at the same volume. Everyone looked the same as they used to. My hairline aside, nothing had changed.

And while this was very nice, in a way, it wasn't quite the emotional experience I'd hoped for. Nobody laughed at old photos of themselves in hilariously dated clothes, because, basically, they were wearing the same outfits now. Nobody felt that enough time had passed to allow them to bury old hatchets, or confess the silly crushes they used to have on anybody else (at least, I assume that's why no one owned up to having had a crush on me). I'd been lied to by every tear-jerking reunion TV movie I'd ever seen. A Twentysomething Guide To Reunions, then: best leave them for a few more years.