Set halfway between the assassination of the Russian royal family and the murder of Dr King, The Revenants is a clumsy attempt to grapple with the conflicts of race and class that has plagued the twentieth century - and continue to complicate UK and USA politics. Set in the English countryside, it imagines a meeting between a black GI and Queen Mary (during WWII, as spitfires fly overhead to remind the audience that there is a clear and present danger). Talk of Nazis, revolution and racism signpost the Big Issues, while the script offers its research in sudden intrusions of detailed information.

Well-meaning, the script fails to deal with the issues effectively: the old queen, and her old queen companion, evince an aristocratic acceptance of diversity, suggesting that racism is really a working-class problem: the angry GI is seduced by their charm, abandons his plan to start a communist revolution and the mention of BlackLivesMatter - along with a finale that transplants the action to a contemporary gospel church service - feels a tokenistic snatch at relevance.

Yet the characters are sympathetic - apart from an off-stage redneck who turns up to arrest the GI - and the cast are strong, bringing life to a plot that simplistically describes the outlines of class and race conflict. The traditional structure, and politeness, of the performance speak of the seriousness and self-consciousness of this slice of political theatre, but it lacks the urgency to expose the roots of hate and prejudice.

Pleasance Dome, until 27 Aug, 5pm, £12.50 (£11).