A Newcastle trolley bus with an orange top, which was the corporation's colour, was repainted yellow to tie in with the film title despite the film being in black and white.
Howard arrives back in London on a BOAC Avro Lancastrian (a converted Lancaster bomber) from Sydney via Darwin, Jakarta, Singapore, Calcutta, Karachi, Cairo and Rome. In the Lake District, the tea room Howard and Simmons call at, the Aira Force Tea Room on Ullswater, is still there. The helicopter chasing Howard and Simmons in the Lake District is a Sikorski R-4, known as the Hoverfly when flown by the RAF and Royal Navy. In Liverpool there are some shots of the Anglican cathedral, started in 1904 but not completed until 1978. There is a decent shot of the long defunct Liverpool Overhead Railway, and in the docks, a Mersey Docks & Harbour Board saddle tank shunting engine.
The first scene of the film depicts Somers returning from somewhere in Eastern Europe in a very shabby and disheveled state, having, it is subsequently revealed, only narrowly escaped from arrest for espionage. In the 21st century, this sequence has usually been deleted from television showings of the film, although it has apparently been restored for a DVD release.
The 'clouded yellow' is a migratory European butterfly.
The chase sequences were filmed in County Durham and Northumberland.