The Charm of Making spoken by Merlin & Morgana is an attempt at Old Irish that translates to: "Serpent's breath, charm of death and life, thy omen of making." The phonetic rendering, as spoken in the movie, is: /ana:l nathrakh, u:rth va:s bethud, dokhje:l djenve:/. In Irish, the phrase is: 'An?il nathrach, ortha bh?is bheatha, do thuar dhéanamh', which is pronounced similarly but not exactly as in the movie.
The initial fight scene in the movie had to be filmed three times. It was filmed at night and the first two times, all the film came out underexposed due to a fault in the exposure meter. The cameraman had a nervous breakdown over the issue and quit.
The names of the 25 knights inscribed on the Winchester Round Table are given as: Galahad, Lancelot du Lac, Gawain, Percivale, Lionell, Bors de Ganis, Kay, Tristram de Lyones, Gareth, Bedivere, Bleoberis, La Cote Male Taile, Lucan, Palomedes, Lamorak, Safer, Pelleas, Hector de Maris, Dagonet, Degore, Brunor le Noir, Le Bel Desconneu, Alymere, and Mordred.
Before the final battle, Arthur's knights are camped around a "Stonehenge" like formation on a hill. The rocks were fake and part of the set. According to John Boorman, some American tourists were driving by down below and saw the formation. Thinking they were real, the tourists hiked up the hill, and Boorman had to explain to them that they were not real but part of a movie set.
All of the armor used in the film was hand made out of aluminum, primarily by British armorer Terry English. English custom-fit the suits of armor for the principal characters, but kept the overall style the same for members of different groups, especially prominent in the nearly "uniform" armor of the Knights of the Round Table. English can be seen in the film during the tourney scenes; he is the blacksmith who looks up at Arthur (Nigel Terry) when the future king is chasing a thief and stops to contemplate filching a sword from the armorers' tent.
The original cut of the film was over three hours long. Among the many scenes that were lost - but was briefly glimpsed in the trailer - was a scene where Lancelot rescued Guenevere from a forest bandit.
The fight between Arthur and Lancelot was filmed on the Powerscourt estate. The battle scenes in Laurence Olivier's film version of Henry V (1944) were also filmed there due to wartime restrictions in England.
John Boorman had planned a film adaptation of the Merlin legend as early as 1969, but the studio he offered it to (United Artists) rejected his concept, offering him The Lord of the Rings instead. When that fell through, he went back to this film.
Nigel Terry was 35 when playing Arthur from a teenager to a 20-to-30-something king, and then finally as an old man. Similarly, 29-year old Cherie Lunghi played Guinevere from teenager to full adult queen to an old woman living out the rest of her life in quiet misery as a nun.
Liam Neeson later went on to play Jedi Master Qui-Gon Jinn in "Star Wars: Episode I - The Phantom Menace"". The legend of King Arthur was one of George Lucas's influences behind his "Star Wars" film franchise. Charley Boorman whom played Young Mordered, his best friend Ewan McGregor played young Obi-Wan Kenobi in the "Star Wars" prequels and is Qui-Gon's Jinn's apprentice, before becoming teacher of Anakin Skywalker.
The graphic scene which Arthur is impaled with Mordred's spear, which Arthur pulls himself towards Mordred was mirrored in "Star Trek: Nemsis". Which Shinzon (Tom Hardy) whom is impaled with a pole pulls himself toward Captain Picard (Patrick Stewart). Patrick Stewart plays Leondegrance.
In real life, Nicholas Clay, Nicol Williamson, Corin Redgrave, Robert Addie and Niall O'Brien all died from cancer. Charley Boorman was diagnosed with testicular cancer in 2010 and became a cancer survivor.
Later, In the original series of the long-running BBC sci-fi series "Doctor Who". The 7th incarnation of The Doctor (Sylvester McCoy) and his companion Ace (Sophie Aldred) encountered Morgana and Mordered from another dimension, which The Doctor is mistaken for Merlin. Nigel Terry would appear in the revived series and Cherie Lunghi would star opposite Billie Piper in "Secret Diary of a Callgirl". Billie Piper played Rose Tyler in the revived series.