This movie was filmed at R.A.F. Upwood. The Lancasters used were NX673, NX679, and NX782. These aircraft also took part in the filming of Les briseurs de barrages (1955).
According to Sir Dirk Bogarde, the character of Tim Mason was based on Wing Commander Guy Gibson, who led the Dambusters raid in May 1943. Gibson was, at one stage, the Commanding Officer of 106 Squadron, and one of the Flight Commanders was Squadron Leader John Wooldridge, co-Writer and Composer for this movie.
Co-writer John Wooldridge - who also wrote the score - was formerly an RAF pilot who who flew 108 missions, reduced to 90 in the film to make it seem more credible; he later wrote in his diary that Dirk Bogarde said to him that it was "the best script he had ever read".
The appointment referred to in the original title, "Appointment in London", is an RAF officer's appointment at Buckingham Palace to receive a medal. The film ends with a dedication - "This story is humbly dedicated to all those airmen who were unable to keep an Appointment in London".