It stars Basil Rathbone as the future King Richard III of England, and Boris Karloff as his fictitious club-footed executioner Mord.

Production went over-budget and led to Lee making a deal with Universal to complete all scenes with the higher costing cast members early to finish the film.

In the 15th century Richard Duke of Gloucester, aided by his clubfooted executioner Mord, eliminates those ahead of him in the line of succession to the throne, then occupied by his brother King Edward IV of England.

Tower of London was originally conceived years before production when the producer and director Rowland V. Lee travelled to England to do research for an epic that involved British history.

[1][3] Rowland V. Lee presented the idea to Universal Pictures and The Hollywood Reporter announced in June 1939 that production was in plans to start.

[3] Art director Jack Otterson developed a recreation of the tower in the studios backlot which involved consulting historical records and original blueprints of the 13th-century building.

[3] The staging of historic battles at Bosworth and Tewkesbury lead to a call for over 300 extras on August 19 and required the production to travel 20 miles north of Hollywood to a ranch in Tarzana.

[3] Lee had the crew move on to film the Battle of Tewkesbury scenes, which involved rain machines that made the extras' cardboard helmets fall apart.

[6] This film, along with Night Key, The Climax, The Strange Door and The Black Castle, was released on DVD in 2006 by Universal Studios as part of The Boris Karloff Collection.

[6] A reviewer in Time found the film "less authentic than its elaborately spooky reproductions of London's Tower...But the battles of Tewkesbury and Bosworth set a new high for realistic racket than should deafen the most demanding".

[6] Frank Nugent of The New York Times found the film "all too painful and pointless" noting that "Karloff can't be taken seriously" and that "even the Rialto's audience, which no one dare accuse of hypsersensitivy, grew silent after a while and stopped applauding Mr. Rathbone's villainies.

[1][9][6] From retrospective reviews, Hans J. Wollstein of AllMovie said that "Karloff employs all kinds of instruments of torture, but very little actual torture is shown" and found that "with the likes of Karloff, Basil Rathbone, and a very young Vincent Price taking turns chewing the scenery, it is also vastly entertaining" as well as that "the battle scenes are so much more intimate and thus interesting for Universal's lack of elaborate staging".