If you think actor Joseph Cullen is cartoonish at the start of this chewy true-life story, you should see the grotesque caricature he becomes. Playing Bulgaria’s wartime king, he is so self-effacing he looks about to crumple down the middle. He is placatory and feeble, the Beano’s Walter the Softy made flesh. The joke in Hannah Hauer-King’s production, written by Cullen and Sasha Wilson, is that nobody in this neglected Balkan country can take themselves seriously. The five-strong ensemble josh their way through silly accents and meta-gags as they send up a nation that knows it will never be a...