The "arena scene" mimics Paget's illustrations from the book.
Inspector Lestrade joins Holmes and Watson for their climactic stakeout in Doyle's novel. However, he does not appear in this movie despite Colin Jeavons's many appearances in that role.
In the Railway scene the "GWR" No.5 is actually former Lambton Collieries No.5, an 0-6-2 Tank Loco Built by Robert Stephenson & Co. Ltd at Darlington (Works No.3377 of 1909). The Lambton Hetton & Joicey Colliery system was part of the large colliery systems in the North East of England, a system so large it even ran its own passenger service.
Kristoffer Tabori's father Don Siegel directed Edward Hardwicke's father Cedric Hardwicke in Uncle Simon (1963) 25 years earlier.