WHETHER by chance or design, coincidence or fate, two plays written by Helen Edmundson are running simultaneously at the West Yorkshire Playhouse.

Helen’s adaptation of Arthur Ransome’s children’s adventure Swallows And Amazons opens tomorrow in a touring production mounted by the Bristol Old Vic in association with the National Theatre and Children’s Touring Partnership.

Meanwhile, the world premiere of her latest commission for Shared Experience, Mary Shelley, her exploration of the radical 19th century novelist and scandalous teenage eloper, is already running in the Courtyard auditorium next door, in a co-production with the Leeds theatre and Nottingham Playhouse.

“They will play to completely different audiences, I would have thought, and they were completely different writing experiences,” says Helen.

Swallows And Amazons, an exotic adventure of savages, dastardly pirates and mortal enemies, is a musical, directed by War Horse director Tom Morris with music by The Divine Comedy’s Neil Hannon.

“Neil wrote the songs and I wrote the play, but we did have to work very closely, which was tricky because Neil lives in Dublin and I live in London, but the good thing was that the National Theatre gave us lots of time over two years,” says Helen.

“So Tom and Neil and I would get together for two-week periods of very intense sessions; five of those sessions in all, sometimes just us, sometimes with the actors as well.”

The creative partnership bonded over a mutual respect for Arthur Ransome.

“There had to be a shared vision of his story of Captain John and his crew setting sail to Wildcat Island,” says Helen. “That vision came gradually but we always knew from the start that we wouldn’t be trying to flood the stage as it’s too risky and too cumbersome.

“We all felt very strongly that we wanted the play to be about children’s imagination and the way they can play invented games and learn about what life is like from playing games. That’s why we have the children creating the world of the play; once we had that concept it was very liberating.”

For Mary Shelley, Helen’s key decision was to focus on her life from 16, when she eloped with Percy Bysshe Shelley, to 18, before she wrote Frankenstein in 1817.

“I quite often focus on strong female characters in my plays, and I thought just how courageous Mary Shelley was,” says Helen.

“A couple of other plays have been written about her, but they focused on her relationship with Shelly and on when she was in Switzerland writing Frankenstein, whereas what I found interesting was her troubled relationship with her father, the political philosopher William Godwin.

“Her problems started with him once she formed her relationship with Shelley, and what she did was to dare to try to live her life to the full and not be held down by expectations that society had of women and the general mores of the time.”

• Swallows And Amazons, Quarry Theatre, tomorrow until Saturday; Mary Shelley, Courtyard Theatre, running until April 7, both at West Yorkshire Playhouse, Leeds. Box office: 0113 213 7700 or online at wyp.org.uk