The U.K. government should dust off a radio system that defended Blighty during the Second World War as a back-up to high-tech GPS.

Back room boffins think that Loran, which is still used by U.K. coastguards, is less vulnerable to jamming than GPS. A panel of MPs was told that the last position system that would be left standing in a terror attack would be the low-frequency Loran, which stands for Long Range Navigation.

A pen-sized device being able to receive GPS could stop ships in a port , but you would need a huge field of transmitters to jam Loran. Loran was originally developed during the Second World War as a maritime navigation aid and is based on the principle of the time difference between signals from a pair of radio transmitters.

The technology has been dusted off after nearly being mothballed because it was not cost effective.