Is there a family more dysfunctional than Gavin and Stacey's? Yes - mine

It is, of course, the glorious moment before the crash. The reason most of us party so hard in the festive season is because they strip everything away from you. The witty friends, the invites, your own fridge. They close the shops and the swimming pool and the cinema. Even the trains stop. Brick by brick, that lovely life you have assembled just collapses.

We should probably go abroad, but there's something about the psychic pull of a family Christmas that makes perfectly sane adults agree to be cooped up together for days, surrounded by tinsel and turkey leftovers.

My sisters and I operate a cunning rota - the only way for grown-ups in their forties to pull off the Christmas trial without murdering each other. We arrive at staggered intervals, so no one has to be relentlessly cheerful all the time. Heavens, sometimes we're never home simultaneously. "Kate is just upstairs," you tell your parents brightly, as you hear her car purr down the road.

"Didn't Liz arrive yesterday?" my sister Ros asks innocently, just as I am catching the last train out of Euston on Christmas Eve, wrapping presents with my teeth.

The trick is to keep busy. By the time I arrive there's only time for Baileys and bed. Next day is an orgy of present unwrapping (if you play it right it can still be going on during the Queen's speech). My mother buys me interesting books about 70-year-old women who change their lives. I buy her books about 40-year-old women who re-invent themselves. Then we silently swap. And everyone, but everyone buys me cat-related ephemera - ignoring my horror of tea towels and notelets and novelty ironing-board covers.

But oh God, this year we're all promising to be frugal. How on earth will we fill the day? Wall-to-wall telly, that's how. My sisters and I sit on the sofa, like three fortysomething cuckoos - an out-take from The Royle Family - waiting to be fed.

Even though my parents have four (count them) DVD players, we'll manage to bicker over whether to watch the box set of Mad Men or the Gavin & Stacey special (the only thing that's getting me through Christmas at the moment).

Two of us didn't feel the need to marry; my younger sister has a girlfriend (the nicest addition to our family). The rest of the year that makes us slightly exotic. But come Christmas it's hard work.

There's something surreal about waking up in your old teenage bedroom in your forties. You lie in the nun-like single bed, surrounded by A-level certificates and posters of Pre-Raphaelite heroines (catnip for depressed teenage girls) and think: "Where is my glamorous life?"

By Boxing Day your parents, still surgically attached to the oven, have started to ask tricky questions about ex-boyfriends. There are two solutions: go out for a long walk or bribe interesting-sounding male friends to ring up "spontaneously".

Meltdown point is Boxing Day at 4pm (no meal pending, dreadful telly). Just be nice. Incredibly suspiciously nice. Always floors them.

By 27 December you're there. Even if Virgin Trains is being suicidally unhelpful, there's coach or carrier pigeon back to London. Your life can start again.

And suddenly - oddly - there's a lump in your throat. Not everyone in their forties has parents they can go back to any more. The cuckoo years are on loan. Memo to self: don't ruffle too many feathers this year.