1910. At the behest of King Edward VII Sherlock Holmes and Dr. Watson set off for Cape Town. The Star of Africa, the largest diamond in the world, is being shipped to England and Holmes is to ensure that it reaches the King safely. In South Africa Holmes discovers that not only is a plan afoot to steal the diamond but the perpetrators are willing to resort to murder to achieve their ends.
An original Sherlock Holmes story, i.e. Not adapted from a book or short story by Sir Arthur Conan Doyle, and it's a mixed bag. On the positive side we have Christopher Lee whose portrayal of Sherlock Holmes is fantastic, giving him a great sense of intelligence and gravitas. The scenery and cinematography are great too, making you feel you really are in Africa in 1910. And yes, some of the scenes were actually filmed at Victoria Falls!
The plot is reasonably interesting though this is where the problems start to come. The film clocks in at over three hours due to the myriad of sub-plots filling up the time. Some of these are needed for the main plot but some are just padding or could have been less elaborate.
The fact that the writer throws in characters like President Roosevelt and Lillie Langtry, shows just how padded some of the sub-plots are. Those particular characters didn't have to be somebody famous but the writers did it just to create a sub-plot out of their fame and for a bit of a wow factor. (Incidentally, Lillie Langtry was 57 years old in 1910 and is 30-something in the movie, so the writer didn't do their research very well).
Overall it's interesting enough to be watchable but with a more focused plot and a decent degree of editing it could have been great.