The Siege of Pinchgut

The Siege of Pinchgut released in the US as Four Desperate Men is a 1959 British thriller filmed on location in Sydney, Australia and directed by Harry Watt. It was the last film produced by Ealing Studios, and was entered into the 9th Berlin International Film Festival where it was nominated for the Golden Bear Award.

Kirk and the others take the Fultons hostage and decide to wait until the following night before leaving again. A boatload of tourists arrives but Pat Fulton manages to act as if everything is normal. However, when a police officer, Constable Macey, visits the fort bringing some milk, Ann Fulton screams for help and the authorities are alerted to the kidnappers presence.A siege situation results, with the police led by Superintendent Hanna. Matt Kirby is initially reluctant to hurt anyone but becomes less stable after his brother Johnny is shot and injured by Constable Macey. Bert, who is an exnaval gunner, realises the gun on Fort Denison could be fired at a nearby munitions ship in the harbour and cause tremendous damage similar to the Bombay Explosion of 1944. However, shells for the gun are locked behind three heavy doors at the bottom of the fort which need to be laboriously prised open. Kirby demands a retrial for his conviction in exchange for not firing the gun. ........

Source: Wikipedia