It was the realistic car chase through the streets of London in this picture, that led to director Peter Yates doing another car chase in San Francisco a year later. Steve McQueen personally wanted Yates for what turned out to be his highest grossing film Bullitt (1968).
The train robbery scenes were filmed at Theddingworth on the Rugby - Market Harborough - Peterborough line. This route had been closed in June 1966 and the tops of the rails were already rusty, so the film crew had to clean and polish them using mops and brushes at the start of filming to make it look as if the rails were still in use.
Jason Robards filmed for 3 days in an attempt by producer Joseph E. Levine to make it more attractive to US moviegoers but in the end, the scenes were deleted.
The location used for the house of Paul (Stanley Baker) and Kate (Joanna Pettet) Clifton, in the scene at the end of the film where the policeman knocks on the door and Kate answers, was Stanley Baker's own house, 7 Queensmere Road, Wimbledon Park. Baker later sold the house and grounds to be redeveloped as the present-day Thursley Gardens.
Like many British tough-guy actors of the 1950s to the 1970s, Robbery star Stanley Baker liked to hang out with real gangsters (see James Morton: Gangland, 1991). It is not meant to suggest that Baker was a criminal himself, but the fact is that actors and rascals in the 1950s and 1960s used to socialise at the same hours of the night, because in Britain in those days the pubs all closed at 10pm, and people who had to work late had to go to late-night clubs to chill out after hours.