Theatre preview: Playwright James Graham on political drama This House

It’s remarkable how often a profound historical shift can depend on a knife-edge decision, one that could so easily – or so it seems – have gone the other way. Think of the few thousand disputed Florida ballot papers that saw George W Bush become US president in 2000, or Britain’s wafer-thin 2016 majority for Brexit. And back in 1979, one of those moments shook Britain, when James Callaghan’s Labour government was defeated in a parliamentary vote of no confidence by just one vote, opening the way for the general election that saw Margaret Thatcher elected Prime Minister, and changed the course of British politics for good.