I confess . . .: Nigel Finch, the writer and director, reveals his weakness for follies to John Lyttle

I build follies in my back garden. I design them, the builder does the work - though I do a lot of the basics: lay the foundation, find the bricks. I've removed architectural detail from various church ruins to the bottom of my garden. There's a doorway from a demolished church down the road. And I brought bricks back from Panama, from the treasury at Portabello. I remember there was trouble at Miami customs.

Traditionally follies are a rich man's foible. But mine are modest. There are only three. Two large ones and a small one, which houses my ferrets. We had Vietnamese pot-bellied pigs living in the largest folly once, until the neighbours complained about the noise. The pigs moved out.

I know follies are meant to symbolise waste or hubris: the very word 'folly' suggests foolhardiness. Still, the whole point of a folly is that it has no point. Actually, even that isn't strictly true. Follies were often part of a gardening politic, an artistic yearning for an Arcadia, a three-dimensonial expression of the age.

There's something heroic about them. They have humanity, humour and intimacy. I see people walking past and staring - their imaginations are stimulated.

Yes, there's another folly in the making. A triumphal arch. Though I'm not quite sure what I'm celebrating.

Nigel Finch is co-editor of BBC2's 'Arena'