When writer Martin Riley was approached after a live theatre performance in a pub and told he should write for television, he was furious, writes Monica Sloan.

After 20 years of writing classic children's TV series, including Gruey, Jackanory and The Worst Witch, he has got over the compliment and overcome his prejudice against television drama.

Now he is helping to break down people's prejudices and misconceptions about opera, with family musical

adventure Gwyneth and the Green Knight, at the Oxford Playhouse next week.

He spent seven years writing the libretto, while composer Lynne Plowman wrote the music.

His Leeds-based musical theatre group Local Brew was performing an earlier adaptation of the legend more than 20 years ago, when a chance remark inspired him to write for television.

Opera the whole family can enjoy . . . Gwyneth and the Green Knight

"We used to used to pretend we were a band so we could get bookings in pubs and we did mini-musicals," he recalls.

"We had just put on a version of Gawain and the Green Knight and a guy said 'That was really good, you ought to write for television'. I was furious, I thought, 'The world doesn't revolve around television, live theatre is the exciting thing and is actually more difficult and sophisticated'. Then when I got home, I thought about it and wondered if I was jealous or afraid. I found out about it and soon after sat down and started writing Gruey, which was later really successful."

His popular adaptations of Jill Murphy's Worst Witch books, currently showing on ITV, have been nominated for a BAFTA and Royal Television Society award.

His next TV series, Bloggarts, is waiting to be aired and he is working on another opera based on the tale of the Pied Piper of Hamlyn.

At 55, he said keeping up with what children enjoy is not difficult, you just need to talk to them and avoid

patronising them.

"Children are a very good audience. They won't watch rubbish and they haven't developed the slightly

hypocritical sense adults have, of 'I want to like this so I will'."

He insists the recitative and lyrics in the opera can be easily heard and understood, to the point where

audiences forget they are watching an opera and just enjoy the retelling of the magical fairytale legend.

The show, performed by Music Theatre Wales and The Royal Opera House, follows the adventures of Gwyneth, a feisty young girl who wants to be a knight at the Round Table. Unfortunately, she can't because she's a girl.

Disguising herself as a boy, she is hired by the young knight Gawain and they embark on a quest through dark forests, mystical lands and King Arthur's Court.

Martin first met Lynne while doing a series of workshops for Opera North. They decided to create something they could not find elsewhere, a funny, accessible opera with strong characters, which children can understand.

Martin draws parallels between Gwyneth and Lynne.

"Lynne is from Ukfield and decided she wanted to be a composer, which isn't an easy thing for a girl to do. Gwyneth is a medieval peasant who's attracted to the idea of Camelot and becoming a knight."

They worked very closely to put the opera together in drips and drabs, while working on other things and living in separate cities.

Martin would generally write the lyrics first and Lynne would set it to music.

"I was living in York and Lynne was living in Cardiff. All the time we were sending it backwards and forwards and she would play bits over the telephone."

Comedy is mixed with scary moments in the show, and Martin has his own theory for why Shakespeare worked comedy into his tragedy plays.

"It was to make sure the audience was still with him," he argues.

"During a tragedy, you can't tell if the audience is moved or asleep, but you can always tell when something is funny."

The show is on July 10 at 7pm. Tickets £11 adults, £8 children, family ticket £32. Box office 01865 305388.