For dramatic effect, the scene where Richard Mansfield changes on stage shows him transitioning from Jekyll to (the more monstrous) Hyde. In reality, Mansfield's transformation was the opposite, from Hyde to Jekyll (more consistent with the depicted scene in Robert Louis Stevenson's novel), and involved standing beneath theatre lights, which made him sweat enough for his make-up to run off his face. A simple, but effective, illusion that, by all accounts, still startled the late-Victorian audience.
Michael Caine was persuaded to return to TV for the first time in nearly 20 years because of David Wickes's powerful script. Caine later described Wickes as "the nicest, fastest Director I've worked for, and the master of filming Victorian London."
In the commentary David Wickes says that when Lewis Collins attacks Ray McAnally in one scene it was thought that the latter had died for some moments. because before Ray McAnally had a major operation before filming.