Directed by Joseph Losey and starring Sam Wanamaker, both of whom had relocated to the UK after being blacklisted from Hollywood by Washington's House UnAmerican Activities Committee, (HUAC).
A poster is seen for Lance Fortune's single, "Be Mine". Lance Fortune was a British singer of the early 1960s.
The song / rhyme used in the prison, "Nick Nack Paddy Whack" (aka "This Old Man"), is a British children's rhyme.
The jewellery store where Bannion takes Suzanne, 'Michael Gosschalk', was a real business in Belgraiva. Michael Gosschalk was noted for making jewellery for a 'glittering clientele', including Princess Margaret.