Goofs

When Shannon meets with Endean and Bobi, in subsequent shots his necktie moves from the left to right side of his shirt.

The train announced as calling at Rugby, Leicester, Loughborough, Nottingham and Sheffield would have been running on the Great Central Railway. This closed to passengers in 1960, long before the time in which the film is set. It would anyway have departed from Marylebone Station rather than Liverpool Street.

Derek wears his former SAS beret incorrectly. He wears it with the flash/peak in the center of his forehead and the sides sloped down to the right and left. Military personnel wear the beret with the flash/crest and corresponding peak over the left eye, and the beret sloping down to the right.

The character portrayed is a mercenary and not "military personnel," thus not subject to any military regulations. Also see Ian Yule's character in The Wild Geese (1978), another mercenary wearing an SAS beret "incorrectly" (and Yule is an actual SAS veteran).

Although they are supposed to be receiving training in the use of the Uzi sub-machine gun, several of the mercenaries who run across the deck to fire at the floating target are armed with Ingram MAC-10's.

The scene at the railway station is set at London's Liverpool Street, made obvious by the Great Eastern Hotel prominently in the background. However, the station announcement says the train is for Rugby, Leicester, Loughborough, Nottingham and Sheffield. Trains do not go from Liverpool Street station to these destinations and did not at the time the film was set. A likelier station for such departure would have been St Pancras.