Question: Who stars as Arthur in the film that Rospo Pallenberg helped?

Context articles: Rospo Pallenberg
Thank You, Jeeves!
The Return of Sherlock Holmes (1929 film)
El Dorado (1966 film)
Candy (1968 film)
Excalibur (film)
Silver Blaze (1937 film)
Dillinger Is Dead
Cutting Class
The Emerald Forest

Rospo Pallenberg is a screenwriter and film director.
 He was involved in the writing of the John Boorman films "", "Excalibur", and "The Emerald Forest".
Thank You, Jeeves!
 is a 1936 comedy film directed by Arthur Greville Collins and written by Stephen Gross and Joseph Hoffman.
 The film stars Arthur Treacher, Virginia Field, David Niven, Lester Matthews, Colin Tapley and John Graham Spacey.
 The film was released on October 4, 1936, by 20th Century Fox.
The Return of Sherlock Holmes is a 1929 American Pre-Code mystery film directed by Basil Dean and written by Arthur Conan Doyle, Basil Dean and Garrett Fort.
 The film shares its title with the third volume of the Sherlock Holmes stories, "The Return of Sherlock Holmes" by Arthur Conan Doyle.
 The film stars Clive Brook, H. Reeves-Smith, Betty Lawford, Charles Hay and Phillips Holmes.
 The film was released October 29, 1929, by Paramount Pictures.
 A copy is held at the Library of Congress.
El Dorado is a 1966 American Western film produced and directed by Howard Hawks and starring John Wayne and Robert Mitchum.
 Written by Leigh Brackett and loosely based on the novel "The Stars in Their Courses" by Harry Brown, the film is about a gunfighter who comes to the aid of an old friend—a drunken sheriff struggling to defend a rancher and his family against another rancher trying to steal their water.
 The gunfighter and drunken sheriff are helped by an aging Indian fighter and a young gambler.
 The supporting cast features James Caan as the young gambler, Charlene Holt, Ed Asner, Paul Fix, Arthur Hunnicutt, Michele Carey, and Christopher George.
Candy is a 1968 sex farce film directed by Christian Marquand based on the 1958 novel by Terry Southern and Mason Hoffenberg, from a screenplay by Buck Henry.
 The film satirizes pornographic stories through the adventures of its naive heroine, Candy, played by Ewa Aulin.
 It stars Marlon Brando, Ewa Aulin, Richard Burton, James Coburn, Walter Matthau, Ringo Starr, John Huston, John Astin, Charles Aznavour, Elsa Martinelli and Enrico Maria Salerno.
 Popular figures such as Sugar Ray Robinson, Anita Pallenberg, Florinda Bolkan, Marilù Tolo, Nicoletta Machiavelli and Umberto Orsini also appear in cameo roles.
Excalibur is a 1981 British epic fantasy film directed, produced, and co-written by John Boorman that retells the legend of King Arthur and the knights of the Round Table, based on the 15th century Arthurian romance "Le Morte d'Arthur" by Thomas Malory.
 It stars Nigel Terry as Arthur, Nicol Williamson as Merlin, Nicholas Clay as Lancelot, Cherie Lunghi as Guenevere, Helen Mirren as Morgana, Liam Neeson as Gawain, Corin Redgrave as Cornwall, and Patrick Stewart as Leondegrance.
 The film is named after the legendary sword of King Arthur that features prominently in Arthurian literature.
 The film's soundtrack features the music of Richard Wagner and Carl Orff, along with an original score by Trevor Jones.
Silver Blaze is a 1937 British, black-and-white crime and mystery film, based loosely on Arthur Conan Doyle's short story "Silver Blaze".
 It was directed by Thomas Bentley, and was produced by Twickenham Film Studios Productions.
 It stars Arthur Wontner as Sherlock Holmes, Ian Fleming as Dr. Watson and Ronald Shiner (uncredited) as Simpson the Stable Boy/Jockey.
 In the United States the film was released in 1941 by Astor Pictures, where it was also known as Murder at the Baskervilles, retitled by distributors to capitalize on the success of the Basil Rathbone Holmes film, "The Hound of the Baskervilles".
Dillinger Is Dead (Italian: Dillinger è morto ) is a 1969 Italian drama directed by Marco Ferreri.
 It stars Michel Piccoli, Anita Pallenberg and Annie Girardot.
 The story is a darkly satiric blend of fantasy and reality.
 It follows a bored, alienated man over the course of one night in his home.
 The title comes from a newspaper headline featured in the film which proclaims the death of the real life American gangster John Dillinger.
Cutting Class is a 1989 American dark comedy slasher film directed by Rospo Pallenberg and written by Steve Slavkin.
 The film was Brad Pitt's first major role.
The Emerald Forest is a 1985 British adventure drama film set in the Brazilian Rainforest that was directed by John Boorman, written by Rospo Pallenberg, and starring Powers Boothe, Meg Foster, and Charley Boorman with supporting roles by Rui Polanah, Tetchie Agbayani, Dira Paes, Estee Chandler, Eduardo Conde.
 It is based on a true story.
 The film was screened out of competition at the 1985 Cannes Film Festival.