If there's anything more excruciating than realising your parents have had sex, it's realising your children are going to have sex.

Such is the embarrassment surrounding the issue it's unlikely to be the first topic of conversation at most family dinner tables. But given the rise in teenage pregnancies and STIs, perhaps it should be.

So suggests Virgins, the latest play by writer/director John Retallack and his award-winning Company of Angels, who arrive at New Wimbledon Studio next week.

Searching for a follow-up to Hannah and Hanna, his acclaimed play about a Kosovan refugee and her British friend, Retallack was inspired to write Virgins by his own experiences as a father.

"My 17-year-old son had a friend over one day when this piece came on the radio about the spread of sexually transmitted infections," he recalls.

"I was shocked by the figures and yet there was this moment of inhibition when I came to discuss it. I ended up bringing it up when they were in the back of the car, via the rear view mirror! I can't believe it is so difficult to talk about."

The story of a family struggling to co-habit and copulate under one roof, Virgins centres around a teenage boy and his first sexual experience, a mother and sister who can talk about sex but not about feelings and a dad who struggles to say anything at all.

"It's a fictional set-up but it could happen to anyone," says Retallack.

"Most of us are brought up in a place with two or three bedrooms, and sex is probably the most important issue in our lives. Especially when you're a teenager, but why not when you're 48 as well?

"This play is about the emotional inhibitions we all face and teenagers' desire for open-ness from their parents."

Like its predecessor, Virgins has been a huge success at this year's Edinburgh Fringe, where its audience applauded Angels' frank, funny and moving approach to a sticky subject. Several sexual health organisations have been in contact saying, 'This is what we have never had before', though Retallack insists the play was never intended as sex education.

He is also keen to defend its use of dance, which perplexed some critics.

"I often find plays are too long and wordy, too articulate in comparison to the way we actually talk," he says.

"There are things you can't say when it comes to sex but that eight or nine minutes of dance can communicate. Actors should be able to express things with their body as well as their voice."

And what of that closest of critics - his own son?

"He's fast asleep as we talk," says Retallack. "But he's coming to see the play in Wimbledon next week!"

  • Virgins, New Wimbledon Theatre, The Broadway, Thursday, September 14, 4.30pm, £7.50/£5; Friday and Saturday, September 15-16, 7.30pm, £10/£7.50, call 0870 , visit newwimbledontheatre. co.uk. Suitable for 13+.