Defence of the Realm is a 1986 British political thriller film directed by David Drury, starring Gabriel Byrne, Greta Scacchi, and Denholm Elliott, with Robbie Coltrane in a supporting role. The film takes its title from the Defence of the Realm Act 1914, passed in the United Kingdom at the start of the First World War, which gave the government wide-ranging powers during the war. The plot mirrors the real-life British spy scandal known as the Profumo affair.