Question: Which film by Reginald Mills was based on a tragic play by William Shakespeare?

Context paragraphs:
Macbeth in popular culture: The figure of Macbeth and related themes from the tragic play by William Shakespeare have appeared in many examples of popular culture since being authored by Shakespeare in the early 16th century.

Hamlet (disambiguation): Hamlet is a tragic play by William Shakespeare.

Othello error: Othello error occurs when a suspicious observer discounts cues of truthfulness.  Essentially the Othello error occurs, Paul Ekman states, "when the lie catcher fails to consider that a truthful person who is under stress may appear to be lying" their non-verbal signals expressing their worry at the possibility of being disbelieved.  A lie-detector or polygraph may be deceived in the same way, by misinterpreting nervous signals from a truthful person.  The error is named after William Shakespeare's tragic play "Othello"; the dynamics between the two main characters, Othello and Desdemona are a particularly notable example of the error in practice.

Hebenon: Hebenon (or hebona) is a botanical substance described in William Shakespeare's tragic play "Hamlet".  The identity and nature of the poison has been a source of speculation for centuries.

Romeo and Juliet (1968 film): Romeo and Juliet is a 1968 British-Italian romance film based on the tragic play of the same name (1591–1595) by William Shakespeare.

Cordelia (King Lear): Cordelia is a fictional character in William Shakespeare's tragic play, "King Lear".  She is the youngest of King Lear's three daughters, and his favourite.  After her elderly father offers her the opportunity to profess her love to him in return for one third of the land in his kingdom, she refuses and is banished for the majority of the play.

Reginald Mills: Reginald "Reggie" Mills (15 September 1912 – July 1990) was an English film editor and one-time film director with more than thirty feature film credits.  Among his prominent films are "The Red Shoes" (1948), for which he received his only Academy Award nomination, "The Servant" (1963), and "Romeo and Juliet" (1968).

The Tales of Beatrix Potter: The Tales of Beatrix Potter (US title: "Peter Rabbit and Tales of Beatrix Potter") is a 1971 ballet film based on the children's stories of English author and illustrator Beatrix Potter.  The film was directed by Reginald Mills, choreographed by Sir Frederick Ashton (who danced the role of Mrs. Tiggy-Winkle), and featured dancers from the Royal Ballet.  The musical score was arranged by John Lanchbery from various sources, such as the operas of Michael Balfe and of Sir Arthur Sullivan, and performed by the Orchestra of the Royal Opera House.  It was designed and co-written by Christine Edzard.

Regan (King Lear): Regan is a fictional character in William Shakespeare's tragic play, "King Lear", named after a King of the Britons recorded by the medieval scribe Geoffrey of Monmouth.

Othello in popular culture: The figure of Othello from the tragic play by William Shakespeare has appeared in many examples of popular culture since being authored by Shakespeare in the early 16th century.

Supporting paragraphs: Reginald Mills Romeo and Juliet (1968 film)
Answer: Romeo and Juliet