An opera starring a schoolboy who persuaded surgeons to let him leave hospital in time to audition for his part has raised £27,000 for the Oxford Children's Hospital Campaign.

Benji CompstonThe professional production held at Summer Fields School, north Oxford, is one of the largest single fundraising events so far for the £15m appeal, and raised more than its target for a blood-taking room at the new development.

Benji Compston, 12, played the lead role in Gian Carlo Menotti's Amahl and the Night Visitors, after winning the part while he was still recovering from a major bowel operation.

The music scholar and school chorister was diagnosed with Crohn's disease three years ago, which left him in severe pain due to inflammation of the gut.

As a result of the treatment he has had at the John Radcliffe Hospital, Headington, his mother Caroline decided to organise the opera to raise money for the dedicated paediatric unit, already being built at the site.

Although Benji knew about the June auditions, he was admitted for vital surgery days before when the Crohn's started to block his intestines.

But he managed to coax hospital staff to let him leave in time for the try outs and successfully won the role after arriving in his pyjamas. During the production, in November, he shared the part of Amahl with school mate Daniel Chaplin, 11.

Benji said: "We are very happy with the amount we've raised. At first we didn't think we'd make enough for the blood taking room, so it was great in the end. The opera went very well and I 'd love to carry on doing stuff like that in the future."

Veronica Warner, of the Oxford Radcliffe Hospitals Charitable Funds, said: "It's a wonderful contribution to the Oxford Children's Hospital Campaign, and we'd like to especially thank Mrs Compston, Benji, Daniel and Summer Fields School."