Clifton takes Robertson to a children's playground so that he can see his wife and child from a distance. As they turn away a river can be seen across the road from them. In the short time it takes them to cross the road to lean on the fence along the river bank the tides gone out.
Moments before the robbers' Jaguar nearly collides with the schoolchildren in Marlborough Hill, NW8, it is seen speeding along Park Lane, which is some two miles away.
The Cessna light aircraft which flies the loot out of the country bears the registration prefix 'EI' ( = Republic of Ireland). This would be very unlikely given that the events take place in England, but was presumably caused by part of the production having been filmed in RoI.
When the 1966 Vanden Plas Princess crashes near the start of the movie at the 7:05 mark, the top view of the impact clearly reveals there is no engine in the car.
When the traffic warden puts the gas canister in the car, a white cable can be seen draping from the inside of the door and this is seen to be connected to the device as he removes it from his bag. There is no sign of the cable in the following close-up shot from his point of view.
When Robinson (Frank Finlay) is getting into Clifton (Stanley Baker's) car, after seeing his wife and child in the park, the sound recordist, wearing a black suit and headphones, can be seen reflected in the car window.
Prior to the opening robbery, the cars drive down High Holborn and then in the next shot turn into Trafalgar Square, which is a couple of miles away.