Klaus Kinski took his role in this movie over an offer to appear in Steven Spielberg's Raiders of the Lost Ark (1981) because he was offered more money. Kinski has said in his autobiography 'All I Need Is Love: A Memoir' aka 'Kinski Uncut: The Autobiography of Klaus Kinski' (1988, 1996) that he thought the screenplay for Raiders was "moronically shitty".
In the home release commentary director Piers Haggard states that stars Oliver Reed and Klaus Kinski hated each other so much during production. Reed would constantly provoke and prank Kinski until he would lose his temper.
Piers Haggard replaced Tobe Hooper as director. At a party at Elaine's Restaurant in Manhattan celebrating the film's release, Klaus Kinski boasted how he and other members of the cast and crew had ganged up on Hooper a couple of weeks into the shoot to get him replaced.
Director Piers Haggard has said of the movie in a 2003 interview for 'Fangoria' magazine: "I took over that at very short notice. Tobe Hooper had been directing it and they had stopped for whatever reason. It hadn't been working. I did see some of his stuff and it didn't look particularly good plus he also had some sort of nervous breakdown or something. So anyway they stopped shooting and offered it to me. Unfortunately I had commitments, I had some commercials to shoot. But anyway I took it over with barely ten days of preparation - which shows. It doesn't become my picture, it's a bit inbetween . . . [actor Oliver Reed was] scary at first because he was always testing you all the time. Difficult but not as difficult as Klaus Kinski. Because Oliver [Reed] actually had a sense of humour. I was rather fine of him; he could be tricky but he was quite warm really. He just played games and was rather macho and so on. Klaus Kinski was very cold. The main problem with the film was that the two didn't get on and they fought like cats. Kinski of course is a fabulous film actor and he's good in the part, the part suits him very well. They were both well cast but it was a very unhappy film. I think Klaus was the problem but then Oliver spent half the movie just trying to rub him up, pulling his leg all the way. There were shouting matches because Oliver just wouldn't let up. None of this is about art. All the things that you're trying to concentrate on tend to slip. So it was not a happy period".
Actor Michael Gough played a character called David Ball who had the same name as the film's snake handler and reptile consultant David Ball from the London Zoo. Gough 's character David Ball in the film is actually based on the real London Zoo Keeper David Ball and was effectively actually named after him.
Publicity for this picture stated from the film's plotline story elements that anti-venom serum treatment from a bite from a Black Mamba snake would only be effective in fifty per cent of any of their snake-bite victims.
The reptile species of dangerous venomous snake in the movie was a "Black Mamba". It's zoological genus name is a "Dendroaspis polylepis". Website Wikipedia states that the Black Mamba "...is a highly venomous snake of the genus Dendroaspis, and is endemic to sub-Saharan Africa. It was first described in 1864 by Albert Günther. Despite its common name, the black mamba takes its name not from the colour of its scales, but from the interior of its mouth, which is inky-black. It is the longest species of venomous snake in Africa, and the second-longest venomous snake in the world after the king cobra. The adult snake's length typically ranges from 2 meters (6.6 ft) to 3 meters (9.8 ft), although larger examples have been recorded. It is also the fastest moving snake in Africa, and one of the fastest moving snakes in the world, capable of moving at 11 km/h (6.8 mph) over short distances. Black mambas breed annually and mating occurs in the early spring."
Some movie posters for the film featured a long blurb that referenced a number of earlier horror-suspense pictures. It stated: "The Mystery of 'The Birds (1963)'. The Danger of "Psycho (1960)". The evil of "The Omen (1976)". The terror of "_Jaws_". Now, the ultimate in suspense".
The movie's closing credits declare: "The Producers wish to extend their thanks to David Ball, overseer of reptiles at London Zoo, without whose skill and courage in the handling of the deadly Black Mamba [snake], this film could not have been made".
The trivia items below may give away important plot points.
Watch the closing credits. The Black Mamba snake leaves a little present for all who do so, a much used typical horror genre story element ending, which is a baby venomous Black Mamba snake just hatched. The final moments set up the possibility of a sequel, although none was forthcoming.
The actors who portrayed the kidnappers were Klaus Kinski, Oliver Reed and Susan George. They all end up getting killed and all get attacked and bitten by the major Black Mamba snake, the latter of which also dies as well.
First of two English hostage thrillers which were released in subsequent years with The Final Option (1982) being the second. Both pictures feature a story element where the police / anti-terrorist squad break into a house through a wall and shoot at least one of the baddies.