From her window, Janet Cresswell, the award-winning playwright who spent 25 years in Broadmoor, can look out on to a Zen garden with rocks arranged around a water feature. This garden is part of her new "home" - Thornford Park, Berkshire, a medium-secure psychiatric unit.

The 72-year-old writer, whose acclaimed play The One Sided Wall was performed at the Bush Theatre in London, was transferred to the unit last year after spending nearly a third of her life with serial killers and rapists, despite the fact she has killed no one. The grandmother was deprived of her liberty after attacking her psychiatrist with a vegetable knife - a serious offence but not one to merit such a lengthy stay in a high-security hospital.

Last week, The Independent on Sunday was able to visit her for the first time, nearly three years after we first highlighted the plight of people left to languish in high-security units because of a shortage of psychiatric beds.

Smartly dressed in black trousers and a patterned blouse, Ms Cresswell managed to joke about her treatment, although she admitted that underneath she is bitter.

"I do feel robbed," said Ms Cresswell, who is receiving treatment for osteoporosis and suffers from tinnitus. "I'm very angry and bitter. It's the system that is making people ill. People just crack up or become depressed. It's too long-winded and heavy-handed."

Ms Cresswell, who won a Koestler award for her writing while in Broadmoor, was transferred to Thornford Park, a private unit run by the Priory Group, for rehabilitation to enable her to eventually live in the community again after years of institutional living.

But she is still under the care of Broadmoor, which has placed her on a "probation" period which the writer recently discovered has been extended by six months, much to her consternation.

Her supporters argue that her case is political, that she has been imprisoned for so long because she is unwilling to co-operate with the hospital authorities. While at Broadmoor, she was repeatedly turned down for release after refusing the supervision of a Home Office psychiatrist because, she argued, she was not mad.

"They said I was paranoid schizophrenic and I objected to that; then they said I was mentally ill. Occupational therapy is now my 'treatment'," says Ms Cresswell, who admits that battling against the system has left her prone to depression.

After the petty privations of Broadmoor, the regime at Thornford Park is far more relaxed. The low-rise brick building looks more like a motel than a psychiatric clinic. The walls are decorated in pale yellows and pastels, the armchairs are covered in soft fabrics, and on the walls hang prints of flowers. Only piped music is missing. The only reminder that patients are not at liberty to leave is the red key symbol on the wall - the inner doors can be opened only with a security pass. There are also ground rules for the men and women who live here, which include no interrupting each other during group therapy sessions.

Located about a mile from the village of Thatcham, Thornford Park was once a school for the children of servicemen at Greenham Common and is surrounded by rather bleak fields. Rabbits come to nibble the grass in the grounds, and Ms Cresswell likes to watch them. But she is still a long way from her family. What she really wants is to live in her own home. "I've never felt so isolated in my life," she says. "Part of the game is to move people around. But it's a three-hour journey for my daughter both ways and it's difficult for her."

At first, the Broadmoor hospital authorities did not allow Ms Cresswell to visit her daughter or to take trips out to the local village or to Newbury, the nearest town. Now, she is allowed out as long as she is with an escort.

"It would be nice to be treated like an adult. Sometimes it feels like a kindergarten here. It [Thornford Park] is so pretentious. You can't go on a shopping trip - it has to be called 'treatment'," she says.

She once thought that she would die in Broadmoor. That is now unlikely to happen. But until her fate is decided, Ms Cresswell is in limbo, unable to "potter around", as she puts it, in a home of her choice or to decide when she wants to eat her meals. At around £3,500 a week, the cost of her incarceration is by no means cheap.

"I've recited my history about 40 times," she says. "I even did a video of my life when I was at Broadmoor. It's all so offensive. I do play their game and I play it back at them. People get into the hands of a psychiatrist and they end up with a label for ever."