Mark Gatiss is superb as Charles I in vivid and human play set at climax of English Civil War

Will there ever be a revolution in Britain? Well, according to playwright Howard Brenton, we’ve already had one – in 1649 – and the country has never been the same since.

His powerful new play cuts straight to the climax of the English Civil War, depicting the final frenzied 55 days of the imprisonment of Charles I, ending with his beheading.

Contrary to his reputation in the history books as a rabble-rouser, Brenton’s Oliver Cromwell, poignantly played by Douglas Henshall, is an indecisive and deeply spiritual man who at one point wonders whether he could win the King over with a “glass of wine and a smile”.

Mark Gatiss is superb as a flamboyant Charles I, the one character permitted to appear in period costume. Director Howard Davies has him playing boules and staggering around the set with a glass of red as he tells everyone to “go to hell”.

Despite the tragedy inherent in the king’s situation, there are some welcome comic moments. In a fictional scene on the eve of Charles’s execution he exchanges remarks with Cromwell about – of all things – the weather. Prosecuting lawyer John Cooke – portrayed by Tom Vaughan-Lawlor – may be the first man in English history to have charged a monarch with “high treason”, but he made the audience laugh with his stutter.

With half of the play set in parliament, the circular stage of the Hampstead Theatre was an ideal setting. The costume choices, however, were irritating: modern suits, Soviet-style black trench coats that constantly reminded the audience it was supposed to be drawing parallels with more recent events.

The cast was enormous – 37 in all – a luxury which added vim to the parliamentary clashes between factions. But far from merely portraying a clash of ideologies, this compelling adaptation manages to resurrect history in a vivid and human way.

* 55 Days is showing at Hampstead Theatre, NW3, until November 24. Tickets: 020 7722 9301.