The song "Look for a Star", used throughout the film during the circus sequences, became a hit pop recording in Great Britain (for Garry Mills) and the United States (for the similarly named Garry Miles). It was written by the young Tony Hatch under his regular pseudonym of Mark Anthony.
The circus where much of the action was filmed belonged to Billy Smart. The boards on the ringside seats, which are in front of the perimeter track and the ring-fence have Billy Smart's initials (BS) on them. Presumably this why Anton Diffring's character has the same initials in order to save the expense of replacing the boards with either nothing on them or have fresh ones made with different letters should Differing have plaid a character with another name.