Howard Brenton’s meaty new history play, set during the final 55 days in the life of Charles I, brings to mind a very modern problem.

It is 1648, England has been mired in murderous civil war for six years and Oliver Cromwell’s New Model Army has just stormed the Parliament it was created to protect. But as today’s western governments have often found, it is a messy business bringing in democracy on the end of a gun.

The main point here, however, is that the ramifications of Charles’s trial and execution are still being felt today. Director Howard Davies underlines the point by setting the 17th-century action, which is performed on a stage of bare boards that bisects the audience, in what feels like a dour 20th- century Britain.

It is a grey world, in which pallid, puritanical and war-weary men, including Douglas Henshall’s doubt-ridden Cromwell, dress in grey and argue over whether Parliament or the Crown is sovereign.

Not a drop of stage blood is spilled, yet the still play evokes a country exhausted by war — a condition which Mark Gatiss’s scarily remote King Charles acknowledges with a dismissive wave of the hand and one word, “pish”.

So speaks God’s representative on earth, as the king believed himself to be. And that aloofness from his fellow man is made all the more stark by the use of costumes — the king is the only character in 17th-century dress,

Charles might have come across as a foppish fool had Gatiss not reined in the temptation to play the role for laughs.

Instead, his king may be part-loon who is convinced that he is God’s anointed one, but there is a chilling political intelligence at work that aborts any impulse to laugh.

Henshall’s Cromwell, meanwhile, is almost gravely ill with the weight of responsibility that goes with dissolving the monarchy. And you can feel the fatigue as he wrestles with the paradox of doing God’s work by bringing down God’s king.

Hurried scene changes, involving serious men moving furniture quickly, lends this talky play a sense of urgency as events move towards Charles’s trial — although it is not quite enough to prevent the first two acts from feeling overlong.

Still, this is a gripping addition to the history play canon, more in the mould of Schiller than Shakespeare.

Although perhaps because in Charles I, Brenton is saddled with an unloveable monarch whose fate is hard to care about, he never generates the tension Schiller achieves with the more likeable Mary Stuart, who was also executed. So the fate we care about here is not so much the king’s or Cromwell’s, but democracy’s. (www.hampsteadtheatre.com)