Final rehearsals are under way at the Sewell Barn in Norwich for the theatre's latest production, Bedlam, by Nell Leyshon, which opens on Thursday.

Set in gin-soaked London in the 18th century, the play chronicles events at the notorious Bethlem psychiatric hospital. It follows the story of a young country girl admitted to the asylum and looks at the terrible treatment administered to its unfortunate inhabitants. Although it is often a tragic tale, there are also moments of lightness and comedy.

'The historical aspect of the play is really interesting,' said director Robert Little. 'It shows the brutality of the way the patients were treated and how far we've come as a society. We see two schools of thought about patient care clearly represented by the two main doctors in the play – Doctor Carew and Doctor Maynard.

'Whereas Carew simply wants to lock patients up to protect society, Maynard is more concerned with trying to help them and even cure them.'

The play features a cast of more than 20 and a small band of musicians playing folk songs from the era.

'I have a reputation for doing ensemble work,' Robert added. 'I love being surrounded by a large number of creative people. The creative journey we all go on, from beginning to end, is really exciting.'

Naomi Miller plays the country girl May Garnett.

'It's a really strong ensemble cast,' she said. 'Rehearsals are going well and there's some great energy and strong dynamics. It's very dark subject matter but we're having a lot of fun doing it. In our performances we're really keen to portray insanity in a way that is respectful and not a cliché.'

The play was originally produced at the Globe theatre in London and was the first play written by a woman to be performed there.

The production is the fourth in the Sewell Barn's 2012/3 season, which will also include productions of Airswimming by Charlotte Jones and When the Rain Stops Falling by Andrew Bovell.

Rehearsals are also under way for the theatre's subsequent production, Silly Cow by Ben Elton, which opens at the theatre in April.

The Sewell Barn is based in the grounds of Sewell Park College (formerly Blyth-Jex school). It has produced more than 200 plays since being founded in 1980.

Bedlam runs from February 21-23 and February 27-March 2. All performances start at 7.30pm and there is a matinee on March 2 at 2.30pm. Tickets can be bought from customer services, second floor, Jarrolds, Norwich, or by phoning 01603 697248.

Visit www.sewellbarn.org for further information.