Rapunzel is being held prisoner in a tower by a wicked enchantress, but there are no knotted sheets conveniently to hand when rescuers arrive. Instead she must lower her golden tresses so that the rescuers can climb up to her. “Rapunzel, Rapunzel, let down your hair,” they cry.

The fairytale story of Rapunzel is being staged as this year’s Creation Theatre Company Christmas show. But in Creation’s version (written by Annie Siddons for Kneehigh Theatre in 2006), a new character appears — a Magic Pig.

“It’s not going to be a fluffy pink farmyard porker but a dark and mysterious boar-like pig, who should be just a touch frightening,” says the show’s director, Charlotte Conquest. “We don’t at first know whether he is on the side of good or evil.”

Responsible for turning the pig into reality is production designer Lucy Wilkinson.

“My vision is that the pig has grown out of the forest, he’s almost a Celtic forest creature,” Lucy told me. “I want him to be both loving and frightening at the same time: that’s the essence of fairytale.”

When I encountered the pig, he was still a skeleton made of curved wooden bones. But the pig was already charging around the rehearsal studio, and had acquired one bodily function that’s guaranteed to make young audience members laugh.

“The pig poos a poo that contains three magic acorns,” Lucy explained.

“Rapunzel finds them, and uses them to help her in times of need. They’re like wishes — she throws them, and they allow her to do things.”

When I went to meet Lucy, she was instantly recognisable. Instead of jewellery, she wears a neatly knotted tape measure round her neck. “I use it as an advertising tool!” she laughed. “I usually have it on when I’m costume shopping — I need to be able to measure things quickly, and it’s the easiest place to keep it.”

Rapunzel rehearsals were taking place in a club in East Oxford. At one end of the building, the pig, and a menacing-looking crow, were weaving their way round human members of the cast. At the other end, Lucy and her team of assistants were busy stitching many and varied pieces of material into costumes and props.

Walking up the Cowley Road, past shops selling everything from old golf balls to burgeoning collections of second-hand clothes, it occurred to me that theatre designers must, surely, need to be inveterate shoppers.

“I do like shopping,” Lucy agreed. “Although, funnily enough, a lot of designers don’t enjoy it: they’ll have an assistant to do it for them. But I think it’s half the fun, searching things out.”

Rapunzel’s hair had already been completed when I visited, and transferred from costume workshop to rehearsal studio, where it was coiled up like a giant snake.

“It’s about 30 metres long,” Lucy told me. “What we want to do is to wind it around the circular stage that we have in the Mirror Tent [Creation are staging the show in the tent used for many previous Christmas shows], and then take it off the stage and out into the front of house. The idea is to create the climbing of the hair through a series of actions, to literally do it horizontally rather than vertically.”

So Rapunzel isn’t going to be escaping from a tall tower?

“We have a tower, although it’s not a great big tower. The tent isn’t tall enough to allow that. I think we can get away with creating a tower which gives a suggestion of height rather than having actual height. But I don’t want to give any more away!”

Lucy started her career as a children’s book illustrator, but found that a very lonely way of not making much money. So she retrained at Bristol Old Vic Theatre School.

“I really love all the different things I have to do as a theatre designer: it goes from initial sketches to technical drawings to making scale models. Then there’s finding and designing costumes, fitting people, and making puppets. It’s all a really interesting way to live my days.”

Rapunzel runs from November 26 to January 15. Tickets: 01865 766266 or creationtheatre.co.uk