The storyline is an unusual one. The Frantz family consist of three short actors, and one who is normal size. They are on tour with Snow White and the Seven Dwarfs, trying to play all the parts between them. And if that isn’t difficult enough, they are somewhere in Eastern Europe in the early 1940s. It’s not long before a Nazi officer appears, and tries to close them down.

But even before the war begins to impinge on the show, all is not well backstage. In her miniature dressing room, shoehorned in underneath the stage itself, effervescent daughter Frieda discovers that her father — a dwarf himself — has decided to hire a full-size, impossibly beautiful, new Snow White, instead of giving the role to her. “You’re a dwarf,” he says testily. “You will never be Snow White.”

Whiter than Snow was originally written by Mike Kenny for Birmingham Rep, and is designed to appeal to audiences from age seven upwards. It has now been taken over by Graeae, a theatre company founded 30 years ago to provide opportunities for disabled actors — and audiences, too, with a sign language interpreter built into the cast.

“I wrote the play because Birmingham Rep wanted a piece for children about science,” Mike explained. “I’m not a scientist, so I didn’t know where to start. Two things happened when I was thinking about the commission. The first was a short article I read in the Daily Mirror, headlined ‘A shortage of dwarfs’. There were so many productions of Snow White being staged that year that there weren’t enough dwarfs to go round.

“At the same time there was a case in the papers about the termination of pregnancies: what were the hormonal reasons for termination.

“I put the two together, and because I’ve worked a lot with children, I took the story of Snow White, which is so much about ‘mirror, mirror on the wall, who in the land is fairest of all?’ — or, if you like, who is the most perfect, the most beautiful? From there, I went on to look at our relationships with our bodies.”

All of which could sound a mite earnest for an evening’s entertainment. But seeing the play on its London opening night, it was very obvious that playwright Kenny is well aware of the need to season a serious message with a lively dose of humour.

“If you’re not entertaining, then your seriousness goes out of the window anyway. Who’s going to come and watch your show?

“I don’t want to be bored or lectured.”

Whiter than Snow is directed by Graeae artistic director Jenny Sealey. She, too, knows how important humour is.

“There was a young man in our audience the other day who is on the autistic spectrum. He found different sorts of humour all through the play. He picked up on things that I, as the director, hadn’t noticed before. In this play, we are laughing with the dwarfs. In a panto you asked to laugh at them. Humour is essential — it’s a coping mechanism, it’s many things.”

Jenny Sealey and Mike Kenny have worked together before several times. I wondered how the collaborative process worked.

“It starts with copious amounts of gin,” Jenny revealed. “Then we get ideas bubbling. We consult a group of actors who we know well, and say, ‘OK, these are the ideas, go away and play’. Then they produce their own ideas, which will fuel Mike’s writing creativity — or sometimes not. Sometimes the actors are more of a bother.

“What we do together is to find out what’s the story, then think about how we’re going to tell that story. Most stories are three-dimensional, and about human beings. And human beings are complex people by their very nature. So one minute we’re laughing out loud, the next minute we’re bawling our eyes out.”

But perhaps the most extraordinary aspect of the Whiter than Snow story is that some of it turned out to be true.

“After I’d begun to write this play, and was creating this family of short people who were doing a show, I came across a piece of research about the Ovitz family,” Mike told me.

“They were a Jewish family of ten siblings from Romania, of whom seven were dwarfs. They called themselves the Lilliput Troupe, and performed in Eastern Europe. They started off at Bar Mitzvahs, weddings, events like that.

“They became quite famous, but the timing couldn’t have been worse. The Second World War began. But they carried on working, even though they did an extraordinarily risky thing: in order not to work on a Friday night, the Jewish Sabbath, one of them would phone in sick. In the end, in 1942, they were betrayed, and sent to Auschwitz.

“They were experimented on by Mengele, and almost treated as his pets. But they are said to be the only family who survived Auschwitz intact.

“It’s uncanny — you can invent a storyline, and then the reality turns out to be even more extraordinary.”

lWhiter than Snow is at the North Wall, South Parade, Oxford, from April 1 to 4. Tickets on 01865 319452 or online at thenorthwall.com