A Northern Irish man has admitted hatching a plot to kill British royal Prince Harry.

Mark David Townley, who changed his named to Ashraf Islam after converting to the Islamic faith, confessed his intention to kill the prince after walking into a police station and giving himself up in May.

A document found on the 31-year -old's computer revealed he planned to disguise himself as a tourist, steal a handgun from an army officer and shoot Prince Harry at close range.

Prosecutor Lynne Townley told Isleworth Crown Court in London, "On May 23, at Hounslow police station, Ashraf Islam made a threat... that he was going to kill another person, that was namely Prince Harry... He said he'd been watching the Horse Guards Parade and planned to disarm an officer while disguised as a tourist, rather than bringing a gun into London. He spent some 10 days in Thailand researching Prince Harry and his whereabouts."

Islam pleaded guilty to a charge of making a threat to kill during a hearing at Uxbridge Magistrates' Court in west London. A sentencing hearing has been adjourned until Nov. 1 so a mental health assessment can be completed.