Were I American, I'm told, I'd already know The Story Of Ferdinand.  A popular book for kids, it tells the tale of a Spanish bull who refuses to fight the matadors who torment him; and while this heart-warming one-man play isn't actually an adaptation of Ferdinand, Munro Leaf's story plays a pivotal role.  Centred on a widowed father and his young but growing son, this is a sweet and highly-watchable production, which nonetheless asks big questions about the values we pass down to our children.

That father, an unremarkable office worker, is played by the impressive Luke Tudball – who at first cuts a diffident and slightly gawky figure, sporting workaday clothes and a spectacularly unfashionable moustache.  He comes to life, however, when he steps away from the open-plan cubicle that dominates the centre of the stage, and opens up the book both he and his young son love.  Its central motif – of the bull who yearns to grow up "big and strong and kind and gentle" – proves a well-developed metaphor for the young boy's life, and also echoes many of the adult characters we meet in the ensuing monologue.

There's a lot packed into Heather Bagnall's 50-minute script; occasionally, I found myself wishing Tudball's open-hearted performance had a little more time to breathe.  That's particularly true when talk turns to the boy's late mother, a storyline which could so easily have been trite but is, in fact, almost unbearably sad.  Yet the most touching themes aren't about life's big events, but concern the small changes that come to us all: the slow but perceptible loss of childhood, the creeping menace of tiredness and frustration, or the way that an uninspiring job can so easily come to dominate a life.

Perhaps a couple of the plot twists are a little on the obvious side, and the conclusion was annoyingly neatly-wrapped for my taste.  But my only real criticism is of the sound effects: the background music is often distracting, and the occasional intrusion of recorded voices tended to remind me that I was only watching a play.  Tudball doesn't need help from anyone else to build a convincing world, and with a few simple script changes he'd be more than able to carry the story on his own.

In the end though, Ferdinand is a powerful and thoughtful play, and while it's billed as suitable for kids aged 7 and up there are messages here for the mums and dads as well.  Bagnall asks some nuanced questions – not just whether being a "real man" means acting like a bull, but also about how mild-mannered people cope when the time to stand up for themselves inevitably comes.  As for me, I'm already big and strong – but I left the theatre newly determined to grow up kind and gentle.  "I got a bit misty-eyed," the proud father says; well, so did I.