In the average person’s lifetime, 20 years are spent sleeping. And while most people enjoy a restful night, some are disrupted by extreme sleep disorders and strange nocturnal behaviour which can be a living nightmare.

Sleep Walkers: Secrets of the Night looks at the disturbing night time activities of four people who are desperate to understand what happens when the bedroom light is switched off.

The programme meets the man suffering from sexsomnia, the woman who eats in her sleep, a little girl who sleep walks and the man who claims to draw in his sleep.

Night-vision cameras are set up in their bedrooms to record them overnight and investigate their nocturnal habits.

Tim, 33, from Ontario, Canada, has sexsomnia – a condition thought to affect around 100,000 people in Britain which causes sufferers to try to have sex while asleep.

Tim and his wife, Amanda, tell the programme that every night they go to bed worried about what Tim will do.

The couple agree to be recorded overnight. On the first night nothing happens, but after the second night Amanda reveals that Tim tried to have sex with her and she complains that he was quite rough.

There are emotional scenes as Tim and Amanda watch the footage and Tim sees for himself what he does during his sleep.

He says: “It’s taken a toll on our relationship. We’re becoming more argumentative. When you don’t realise that you have a problem it brings out the sad person inside. Because inside me there is a person and well, sometimes it feels like he’s by himself.

“It’s you, you’ve got the problem, ‘you’re a weirdo, you’re a freak’. It’s like Jekyll and Hyde.”

One in ten people sleep walk and this has been a problem for nine-year-old Olivia from Hampshire since she was just three.

Her mum tells the programme that she is worried about the condition affecting Olivia’s life as she gets older and wants to stay over with friends or have a boyfriend.

Olivia is filmed over night and then visits a specialist who thinks waking her up throughout the course of the night might help. Olivia’s mum tries this technique and reveals the results to the programme.

Canadian Xanthe estimates that she eats approximately 150 meals a year in her sleep. She frequently wakes in a morning to discover that during the night she has got out of bed, walked to the kitchen and made herself a meal without even waking up.

She has been known to make anything from pasta to sandwiches and sometimes takes the food into the bedroom to eat on the edge of the bed while her husband sleeps.

Xanthe tells the programme that she struggles to control her weight because she eats healthily through the day but then eats too much at night.

The film features footage of Xanthe making her midnight snacks in the kitchen and she is emotional when she watches the tapes back.

She says: “I’ve never seen it before. I’ve seen it in terms of feeling like I was watching myself do it, but I’d never physically seen it before.

“I’m not crazy, it is actually happening, because for a long time I actually thought, ‘It’s not actually happening, these are just horrible dreams.’ But now it’s proof. It’s almost physical proof that it’s not just a horrible dream that I’ve been having.”

And the programme features Lee Hadwin from North Wales who believes he has been drawing in his sleep for the past 20 years.

He tells the film that he started sleep walking when he was four. When he was a teenager his parents caught him drawing under the stairs and it has continued from then.

Lee claims he can’t draw when he is awake and he has never been to art college or studied the subject, yet in the last 20 years he says he has created 40 drawings during the night. The film features footage recorded by Lee’s partner, Clint, of him apparently drawing in his sleep.

But experts claim this has never been heard of before so Lee agrees to be filmed and have his brainwaves monitored overnight to see if he is actually asleep when he draws. The documentary cameras fail to capture anything, so Lee visits a leading sleep clinic where the footage taken by Clint is examined..

Doctor Chris Itsikovsky from The Edinburgh Sleep Centre says: “If I think about people who eat when they’re in a sleepwalking state they tend to be quite messy in terms of how they eat.

“They may be able to use knives and forks but probably they’re likely to chop at their fingers as well. So one doesn’t expect finely tuned co-ordinated behaviour, and that’s where he becomes interesting.”

As he closely examined the footage Clint took of Lee drawing in the night, Dr Itsikovsky says: “I think that bit is interesting, as if he’s looking at something. When he was looking at the drawing there he’s sort of looking as if he’s appreciating what the drawing is about, and there’s some facial gestures in there.

“It’s not the usual blank, emotionless, fixed stare that one gets from a sleep walker. Then, on the other hand, most are not drawing either.”

Lee stays overnight at the sleep clinic and is monitored but once again the equipment fails to capture him drawing in his sleep. Dr Itsikovsky says he think Lee may be suffering from a split personality disorder brought on by the death of a close friend when Lee was a teenager.

The film follows Lee as he visits a therapist to discover what exactly is happening when he draws.

Lee has spent the last 20 years claiming to be a sleep walking artist – could this be the explanation he has been waiting for?

Tuesday, 16 December 2008, 9:00PM – 10:00PM ITV1