The difference between a flower girl and a duchess is not the way she behaves, says Eliza Doolittle, it is the way she is treated.

Shaw's brilliantly witty play about class, middle class morality and the treatment of women is always worth seeing and always worth staging. Sadly, this production is mostly on the level of a good amateur show. (Not a student show, they would have given it more zip.) There are only pockets of humour - which is a shame when the playwright's wit goes right through every scene. Overall, it lacks chemistry. This is a pleasant way to spend an evening and the audience appreciated what they saw but it's a Pygmalion without punch. It could have been so much better.

It's all very well casting an impressionist in a lead role if what you want to see is an impression of actor. Alistair McGowan has not worked out who Henry Higgins is. He gives us glimpses of gawky schoolboy and bursts of bombastic bully but nothing believable. I didn't believe he was a professor, I didn't believe he cared about phonetics. I didn't believe the actor had researched the lives of bachelor professors in 1912 - or now because some of them won't be that different. McGowan hasn't grasped the difference between acting and parody.

Despite what happened later when it inspired the musical My Fair Lady, Shaw did not write a romantic ending. This play is about women's independence, it's not a Mills and Boon. When Higgins has the last line, saying that Eliza will do what he wants, actually he knows - by then - that she won't. She no longer needs him and that's her victory over him. This should be the powerful ending of the play but McGowan's Higgins doesn't have the depth to deliver it.

Rachel Barry creates a sweet Eliza that we can sympathise with and love, she brings out the poignancy of the role, but there could be more of the humour and the grit. Eliza is a street trader, a girl who made her living, as she says, selling flowers but never herself. We should know how hard that is. She has lived on her wits and has defended herself against much tougher types than puffed up Higgins, which is why she gets the better of him in the end. After all, it is she who comes to him asking for elocution lessons and prepared to pay for them because she wants to better herself and open a flower shop. She has her pride and her ambition. This is a sparky part and I would have liked to see the actress have more fun with it. The "awls" are overdone so they are shrieks rather than expressions of indignation.

There are accomplished and natural performances from Rula Lenska as Higgins' mother (who deserved a dress that knew whether it was evening or afternoon and at least one change) and Paul Brightwell as his friend, Colonel Pickering.

Jamie Foreman as Alfred Doolittle, Eliza's father, is the highlight of the show. Doolittle's lament that he had a much better time as "the undeserving poor" when he could touch anyone for money - than with his unexpected wealth because now everyone is taking money off him - is a bit of a joy. At last, Shaw's spirit seems to shine through.