Dirk Bogarde persuaded Margaret Lockwood to co star. "I was dubious about being able to play such a character, though I liked her honesty," said Lockwood. "I think it was a very interesting plot, very claustrophobic," said Lewis Gilbert. "I think it was the best thing Margaret Lockwood did, she was great in the film."
When Edward tells Freda that she should have checked up on him with "Somerset House", he is referring to the fact that it then housed the Public Records Office where one could see any deceased person's will.
"I'm glad I did it, but am still wondering exactly where it got me," said Margaret Lockwood in 1973. After making the movie, she did not appear in a feature film for another 21 years.
The Health & Strength magazine Edward is reading in the seaside restaurant is a real periodical. It is the April 14, 1955 (volume 84, number 8) issue, featuring Reuben Govender from India on the cover. The price was 1 shilling (1/20th of a pound, or about $2.00 in 2022). The use of this magazine may allude to Edward's sexuality.
Edward's convertible is a 1955 Sunbeam Mark III.