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 minor role.

Dennis Markham (Ian Bannen), a prominent Member of Parliament (MP), is reported by a London paper to have been seen leaving a woman's home on the same evening as she is visited by a military attaché from East Germany.

Vernon Bayliss (Denholm Elliott), Nick Mullen (Gabriel Byrne) and Jack Macleod (Bill Paterson) all work together for the Daily Despatch.

Mullen visits the young man in prison (caught by police at the start of the film) telling him that his accomplice is dead.

This leads him to go to the site where the film began; a high security, but seemingly unmanned military base actually run by the USAF near the village of Brandon.

Moreover, the newspaper owner, Kingsbrook (a character akin to Lord Beaverbrook), has personally intervened to make sure it isn't published.

Here he is needed to suggest integrity and scruples, and does it almost simply by the way he looks... Defence of the Realm ends on a bleak and cynical note – unless you count the somewhat contrived epilogue – and gets there with intelligence and a sharp, bitter edge.

"[3] Radio Times gave the film four stars out of five, writing, "The role of the sozzled veteran reporter who for once finds himself involved in a meaningful story is brought wonderfully to life by Denholm Elliott... Gabriel Byrne, as Elliott's ambitious young colleague, is less effective, but the film has plenty of tension and co-star Greta Scacchi proves a worthy accomplice.