According to Sir Christopher Lee, the pond fording at Black Park was a horrible experience. The water was polluted and the bottom consisted of three or four feet of mud, sludge, broken trees and branches, stench, and general filth that the stuntmen refused to do it. Michael Ripper nearly drowned, Oliver Reed contracted an eye and ear infection, and Lee claims he couldn't walk upstairs for nearly six months because of the after-effects.
Oliver Reed got an ear infection and had to be hospitalized after participating in a sequence that was shot in the filthy waters of a river.
When approached by Michael Carreras to write a script for a pirate movie, Jimmy Sangster was cautioned by the producer that they couldn't afford a ship. The ship seen from long shot in the beginning was a stock shot.
Kerwin Mathews (Jonathon Standing) played the son of Andrew Keir (Jason Standing) in the film. However, in real life, Mathews was three months older than Keir. They were born on January 8, 1926 and April 3, 1926 respectively.
The penal colony where Jonathon Standing (Kerwin Mathews) was sent to was also the Callow Hill Location. The scene of his escape and his attempted killing by two men was shot in one of the swamps at Burnham Beeches. Other scenes of the pirates wading through the swamp and walking in wooded areas was a combination of Burnham Beeches and Black Park.