Review: HR Haitch (Union Theatre)

There is something truly exhilarating about seeing an exciting, unique stage performer for the first time. I'm talking about Tori Allen-Martin, a one-woman powder keg of charm, talent and comic chutzpah, the like of which comes along all too seldom. As ballsy, glamorous, social media savvy East End girl Chelsea – as big of heart as she is of mouth – she is the magnetic centre of this new British musical, and she is an absolute sensation. When singing, she has a sweetness and power that nicely balances her brash, hilarious line delivery, while her ability to turn on the pathos when required further ensures that Chelsea, this stroppy, outrageous publican's daughter, never becomes remotely obnoxious. She is beautiful, and she is a natural clown: she is something very special indeed.

Allen-Martin has undeniable star quality for sure, and she also, fortunately for us in the audience, displays a true star's ability to rise above some decidedly iffy material. It's not that Maz Evans (book and lyrics) and composer Luke Bateman's slight comedy musical isn't fun – it mostly is – but it is pretty rough-round-the-edges, and could lose a good twenty minutes playing time. Set in a parallel version of London at the time of the last Olympics, it features a cute but dumb Royal Prince (delightful Christian James, who effortlessly fields a glorious bell-like tenor) in disguise as a commoner and falling for the adorable Chelsea, a vehement anti-Royalist whose widower father's East End pub is under threat by money-grabbing developers.

Throw in a nymphomaniac granny, a royal father clearly channelling Prince Charles, a guilt-ridden PM with a secret, and a nasty Princess determined to bag the throne for herself, and you get something that resembles a crude, intermittently wonderful mash-up of Carry On, Whitehall farce, My Fair Lady, and the musicals of Lionel Bart. There are a number of running jokes, including a pun-heavy one about Brexit, that range in quality from inspired to dreadful, and a pervasive foul-mouthed jollity that starts to wear a little thin after more than two hours of Daniel Winder's nimble production.

Bateman's tunes are bouncy but unmemorable though Evans' lyrics are excellent – funny and incisive – and there is a duet for Chelsea and her Dad where they recall previous Christmases when their family was complete, that brings a genuine lump to the throat. It is refreshing to see a musical that in no way aspires to take on Broadway or the West End, although the act one finale cheekily references "One Day More" from Les Mis as the various characters simultaneously but separately outline their respective hopes and dreams.

Christopher Lyne does magnificent, impressively contrasting work as Chelsea's soft-hearted Dad and nice-but-dim Prince Richard, while Andrea Miller has a ball as a gleefully venomous version of the ruling monarch and also as Cockney Vera, 69 years young and running a dirty chat line from her mobile. Emily Jane Kerr is amusingly manic and sings up a storm as the scheming Princess, and Prince Plockey delivers a superb double as the PM and Chelsea's wayward West Indian uncle.

Winning as the rest of the cast are, and entertaining as the piece itself is, I suspect the whole show would be a lot less bearable without Allen-Martin's irresistible presence. She elevates a raucously enjoyable, cheerfully mediocre piece into something fine and funny.