Rasputin, Bristol Old Vic

Previous shows by the Natural Theatre Company have taken the form of a revue filled with musical numbers and a storyline that rapidly evaporates under the intense heat of comic mayhem. With Rasputin, they have moved up a level, away from the audience participation, the overblown gestures, and the chaotic echo of the street theatre where the Naturals were born. This is a true musical, with powerful songs that move the narrative on, and a strong plot inspired by history, albeit with a generous sprinkling of poetic licence.

In the Naturals' reality, for example, it is not the Tsarevich to whom Rasputin applies his mystical healing powers to win the Tsarina's favour, but her dog Pushkin. The music reverberates with Rimsky-Korsakov and Mussorgsky, and the stage drips with bleak Russian melancholy and onion domes. However, it sounds like a few Sondheim recordings may have slipped into the stack of Russian classical and folk music from which the composer Christopher Dickens sought inspiration. But in a way, the echoes of Sondheim in both the music and the witty intricate lyrics are no surprise: he is one of the few contemporary writers of musicals who is secure enough to admit humour and silliness into his work. And humour and silliness are very much the Naturals' bread and butter.

As a result, many of the historical characters from the Rasputin story will be spinning in their graves at their portrayal. Jill Myers' depiction of an intensely batty Tsarina is especially riveting, particularly when she accompanies herself on the trumpet. Yet research by Dickens and his co-writer Ralph Oswick has come up with many facts more surreal than even the most fertile imagination could produce (Prince Felix Yusupov, the man who finally killed Rasputin, really was a rampant transvestite who liked to dress up for society balls).

Oswick also takes the title role, and complements his intimidating Rasputin with a performance as Mrs Rasputin that highlights once again that he is a pantomime dame manqué. However, with so many characters to portray with a cast of seven, cross-dressing is all the rage in this production. Admirably, the actors – Christian Edwards in particular – prefer to get their laughs through smooth characterisation rather the fact that they are men in dresses. As if excellent comic performances and astonishingly fast costume-changes were not enough, the cast also accompany themselves on trumpets, flutes and guitars.

While the Natural Theatre Company in the past stuck to being brash, loud, and utterly inconsequential, Rasputin is far more than that. It is an intelligent yet totally silly musical that combines a few moments of genuine bleakness with some perfectly timed comedy, and a score that bubbles like the Neva in spring. It's the Rasputin musical Sondheim hasn't yet had a chance to write.

Touring next year to Bury St Edmunds, Winchester, Huddersfield, and Bexhill