This film's 'Triple Echo' title refers to the triple echo sound from a shotgun fired at the climax of the movie.
Halliwell's Film Guide and John Willis' Film Annual 1973 list the film without the definite article. It is first heard in the beginning of the movie: three echoes wherein the title is shown at the same time.
The band in the dance scene were members of the Band of The Royal Hussars (PWO) as well as other ranks of the regiment playing various extras. A friend of Private rank (Trooper) played an RAF SNCO.
Final film of Daphne Heard.
Oliver Reed and Glenda Jackson had previously starred in Women in Love.