In this climate of fashionable political cynicism, it has become all too easy to sneer at the Left-wing convictions of playwright Howard Brenton, who, unlike his chum David Hare, has not embraced the theatrical centre ground, or indeed a knighthood.

It can't be denied, though, that this dry piece of 1970s agitprop doesn't make for a scintillating evening, as it lashes out variously at Communism, the ill-disciplined militancy of British workers and the inefficacy of trades unions.

It's intriguing to see the parallels between these weapons of middling distraction and Tom Stoppard's Rock and Roll.

Both works feature English Communists unhappy to have their Russian-red tinted spectacles wiped clean by the personal testimony of someone who has experienced the brutalities of the Czech Communist regime.

The difference is that Stoppard fashioned a compelling drama from this clash of real and ideal, whereas Brenton offers only notes towards such a piece.

It's 1976 and the labour relations are fractious. Closure is threatened for a small London crisp factory. Its workforce wants union representation but the union doesn't seem to want them.

Eventually, a group of teenagers high on hard-Left talk occupy the building, dragging with them co-worker Josef Frank, who was in reality executed in a 1952 Prague show trial.

The action cuts awkwardly between 1952 and 1976, London and Prague, with the unfortunate result that both narrative strands end up feeling under-woven.

The dramatis personae are not so much characters as stops on the bus route of British society. The best of the lot is young firebrand Janice (sparky Katie Cotterell) but we're not entirely sure what stokes her revolutionary zeal.

Director Nathan Curry keeps the momentum up but there will be no jubilant massed singing of The International here.

• Until 23 Feb (0844 847 1652, www.finboroughtheatre.co.uk).