RICHARD FORESTER, barrister: Penetrative heterosexual intercourse probably crosses my mind once every half an hour - it depends on who I'm with.

CHRISTINA DODWELL, explorer: There's some extraordinary statistic about the amount of mental energy that gets lost in thinking about sex. You forget about it when you are travelling, and you free up a whole mass of mental energy. Celibacy should probably be tried by everybody.

JOHN LESLIE, TV presenter: I think about sex on Tuesdays around 4pm. That's the absolute truth.

ROBERT ELMS, journalist: A lot, especially if I'm not having much. I have no qualms about telling the truth about my sex life, in fact I love filling in sex questionnaires in magazines.

STEPHEN BOURNE, TV archivist: Most of the time - well, maybe not every day, but a lot.

AMANDA BATES, wife and mother: I don't have time to think about it very often because I've got a one-year-old child. At the moment my sex life is not too good - I'd say once a week plus, depending on my child's sleeping pattern.

FRED STUART, window cleaner: Every day of the week when I see all the young girls in the offices. At 63 I'm getting to the age now where I think about it rather than do it]

KATHARINE HOYLE, owner SH, an erotic emporium for women: 11.30 to 6.30 six days a week. I live, breathe and work sex - other people's sex lives anyway.

PETER TOVEY, health advisor/HIV counsellor: That depends on my mood, my mental state and my health; sometimes a lot and sometimes never at all.

KATE BRANCH, club promoter: Every day. Actually, I think about it more when I'm getting it.

JAMES McDONNELL, hair stylist: I don't really think about it during the day, but we talk about it a lot at work. EastEnders or sex is all we gossip about in the staff room.

DAN REBELLATO, playwright and university lecturer: Oh, well not all that much really, not as I get older anyway.

LINDA VALENTINE, Virgin Publishing employee: All the time. When I'm not thinking about it I'm having it. I think the norm is four times a week - it can be in one go, though.

JOHN DROVER, chartered surveyor: Every time I see an attractive woman. I work in the West End where there are quite a few - so I would say a couple of hundred times a day.

CLAIRE PROWSE, trainee teacher: I do think about sex, no surprises there - but at the moment I'm not feeling well so I have more pressing things on my mind.

JIM BROWN, plumber: About every 20 minutes. I think about it all the time, day and night. I am a young 47 and married, and still do it on a regular basis.

(Photograph omitted)