Morpurgo's acting dream comes true in War Horse

It is the fulfilment of a lifelong ambition for Morpurgo, 65, who has always dreamed of following in his parents' footsteps.

His minor walk-on role in the final night of War Horse at the National Theatre will see him join a succession of family performers stretching back to a great-grandmother who sang for Queen Victoria.

"I come from a very long line of actors. My mother was an actor and my father was an actor and they met at Rada. It's what I wished I had done," he said.

"I've come to theatre very late in life, from the outside, with my books being adapted. But I love the camaraderie and this extraordinary risk they take every night, getting the audience to suspend their disbelief."

The evening will be particularly poignant as the last outing he enjoyed with his mother, Catherine Cammaerts, before she died 15 years ago in her seventies, was to the National to see a version of his book, Jo-Jo The Melon Donkey.

Cammaerts gave up acting when she had Pieter, Michael's elder brother, and Michael. And it will also be a tribute to his father, Tony van Bridge, whom he met only in adulthood as his parents separated when he was very young.

Van Bridge, who died in 2004 aged 87, moved to Canada where he worked with award-winning director Tyrone Guthrie, becoming one of the country's best-known comedy performers. Before that he had appeared in numerous TV shows from The Avengers to Mission Impossible.

"Because he had been away during the war, I didn't know him, so when my parents split up he did this rather wonderful thing and let his children grow up in a new family," Morpurgo said.

"At that time, divorce was taboo and nobody spoke about him because they just wanted to airbrush him out."

Morpurgo was 19 when he first saw his father perform as Magwitch in a TV production of Charles Dickens's Great Expectations one Christmas. Morpurgo said he believed his parents would have loved to see his own brief appearance, which was arranged as a present by his wife, Clare.

"I do have a bit of an ache that my father and my mother aren't here to see it," he said.

"Things have come a little bit full circle. I know I shall be laughing inside, but probably crying as well."

Morpurgo grew up in London as well as Sussex and Canterbury. He lives in Devon with Clare, although they also have a flat in Fulham. They have three children, two boys and an adopted girl.

War Horse was originally published 27 years ago, but the former Children's Laureate's books are currently much in vogue in the theatre.

Private Peaceful, When The Whales Came and The Mozart Question have all been adapted for the stage.

War Horse is transferring to the New London Theatre, Drury Lane, from 28 March.