Other mistake: It's not possible for Holmes to remove all of his elderly bookkeeper disguise in the mere seconds Watson turned his back.
The Return of Sherlock Holmes (1986)
1 other mistake in season 1 - chronological order
Starring: Jeremy Brett, Rosalie Williams, Edward Hardwicke
Factual error: Holmes and Watson walks through a colonnade. Clearly visible in the background right over Watson's head is part of a 20th century circular red and white road sign. (00:34:18)