Sarah Weller is not very comfortable in pants. 'If I go out tonight, I won't be wearing any,' she purrs, 'though I might put on suspenders.' An odd confession for the lady who has become the face (and finely-toned bottom) of the naughty new M&S underwear range.

'Well you don't need sexy lingerie to be sexy,' she explains. 'I feel horniest in little white schoolgirl pants. But whatever you wear should reflect your mood. My mum got me a set of knickers with a different slogan on each one - 'Gorgeous', 'Naughty', 'Excitable', that kind of thing - so my boyfriend always knows what he's in for. Except there isn't one with 'Fuck off, I've got my period' on.'

Lucky him. But where does Sarah stand on the perennial M&S debate? Clobber or grub? 'Grub, definitely. I love the Marks roast chicken sandwich. But food can be sexy too - you can have a lot of fun with melted Belgian chocolates - although I don't think I'd try anything with the chicken sandwich. That said, I did once experiment with some carrots... I put them back in the fridge afterwards. My then-boyfriend's parents' fridge, as it happens.'

But hasn't her vegetable sex obsession got her into trouble at M&S? 'No, I've managed to contain myself. I haven't had to rush into the changing rooms for impulsive sex - yet. But yuck, think of all those security guards watching you! No, the naughtiest thing I've ever done in a shop is pilfering pick 'n' mix from Sainsbury's.'

And now she has successfully sexed-up boring old M&S, what next? Raunching up Railtrack? Saucing up Songs Of Praise? 'Yeah, I could give it a go. Put my hair up all prim, with spectacles and a nun's outfit - and then lingerie down below... ' Sounds good, go on. 'I can't say any more. My dad's a subscriber to Maxim, and he's going to read every word.' Er, sorry, Mr Weller. She started it.