The past is a foreign country: it always snows at Christmas there. Michaelmas term, and the off-grey duvet of cloud begins to discharge a few grubby feathers during morning break. At lunch time, we convene in the already whitened field, where the M twins, a dour pair from the Arabian Gulf, are holding up clumps of cold crystals in their bemused idiot-savant way, having never seen snow before. This pair have proved impossible to please in their short tenure here: inconsolably homesick, proud and shy, rebuffing any attempts to make friends. Now their slow, solemn smiles come, as they rub the mush against their cheeks, form floppy, experimental snowballs, listen to the new silence and bathe in the silvery light which seems to pulse from the ground and not the sky.

Watching them cautiously pelt one another, we begin to think they're not so bad after all. One of the twins murmurs something about a proper, traditional Christmas, and the idea bubbles forth: we must have our own Christmas tree! "For the twins," we say, half-patronising, but the truth is that though most of us are hardbitten old lags, their doleful demeanour is making everyone feel a little homesick. Bounding the school on three sides is a forest of protected pines. We will simply push our way in and pull up a small one. Accordingly, after tea we don our woollies and knee socks, our hats, mittens and duffle coats and stomp out. It would be most unusual even on a balmy summer's evening for almost the entire house to be going out for a casual stroll together, so it's positively bizarre on a bleak, cold night with flakes of snow still in the air. The personnel of the house changed constantly over the two years I spent there, but we must have been a pleasingly multi-cultural crew: Hanan from Cairo, perhaps, and Fiona from Liverpool; Zora from Iran and Karen from Sheffield; maybe even the Colombian princess, a girl whose spell with us turns out to be very brief indeed: tall, striking, rich, speaking four languages fluently, exquisitely dressed and unnervingly grown-up, thrown out of half a dozen boarding schools, she carries on a full sexual relationship with her much-older boyfriend at weekends in a nearby hotel. This when the rest of us think ourselves greatly daring if we take off our tops in a boy's study with the lights out.

So perhaps the Colombian Princess is there, wearing the sort of winter gear more often seen in Gstaad than the Pennines. The motley crew stumbles along the rutted path to the woods in the fast-fading light. A few of the girls have brought torches, but our first plan of pushing into the centre where a little tree is less likely to be missed is quickly abandoned. It is horribly sinister in there, with every snow-frosted heap of needles seeming to cover a hidden pit. There don't seem to be any baby Christmas trees. The chatter fades out; we'd all feel a bit feeble going back empty- handed.

Twin A suggests that instead of uprooting a small tree, we "knock the top off" a big one. The more conservation-minded chirrup in disapproval, but Twin B promptly begins not so much to climb, as to wrestle her way up a tree which is slightly less lofty than all the rest. Her Wellingtons recede into the darkness, there are snapping sounds and low curses from above, while the whole trunk shudders, then suddenly she abseils back down like Supergirl with the tree-top in one hand, using it as a brake. We didn't high-five in those days, but there's a certain amount of backslapping before we set off to drag the thing home.

It has a curious property, that tree: it gets bigger and bigger, the closer we get to the school, and not just because we are sweeping up stones, mud, leaves and snow in its branches. What looked little more than a bundle of twigs in the forest proves difficult to get through the front door. We scratch and scrape and scrawp it up the hall and into the sitting room, which it almost fills. It seems terribly pagan, lurking like Heathcliff between the piano and the sofa. It is going to be terribly difficult to pass it off as "just something we picked up on a walk", but fortunately the Housemistress's eyes light up with crafty glee when she spots it. Wisely deciding not to ask too many questions about provenance, she bags it for her own household after the end of term.