There have been many adaptations of Sherlock Holmes over the years, on film, TV, and radio. But the series of dramatizations done by The BBC for Radio 4 between 1989 and 1998 are unique in that the Beeb managed to do what nobody has done before or since — they adapted every one of the fifty-six short stories and four novels by Sir Arthur Conan Doyle and each production featured the same actors playing Holmes and Watson — Clive Merrison and the late Michael Williams (Judi Dench's husband). The series was produced and chiefly adapted by Bert Coules.
The series was so popular that the BBC commissioned Coules to produce and write a series of pastiches entitled The Further Adventures of Sherlock Holmes which ran for four seasons from 2002 to 2010 with Andrew Sachs playing Watson, due to Michael Williams' passing in 2001.
Also of interest is Bert Coules' book about producing and writing the program — 221 BBC: Writing for the World's Only Complete Dramatised Canon and Beyond available for purchase from here.
- Adaptational Heroism: Lucretia Venucci. In the story "The Six Napoleons" she was responsible for giving the Borgia Pearl to Beppo. Here she's completely innocent.
- Adaptational Villainy: Professor Corim in "The Golden Pince-Nez" who goads his wife into suicide by talking about the unfaithful wife in Anna Karenina.
- Adaptation Expansion: Occasionally, like with "The Mazarin Stone".
- Back for the Finale: Both Lestrade and Mycroft make small appearances in the "The Retired Colourman".
- The Cameo: Judi Dench plays Mrs. Hudson in one scene in "The Hound of the Baskervilles".
- Death by Adaptation:
- Mary Morstan. In Doyle's stories it's never explicitly said that she died, only that Dr. Watson suffered a "sad bereavement". Here, her deathbed is the opening scene to "The Empty House".
- Lucretia Venucci. She was the primary police suspect and she later hangs herself in her cell, due to the police's refusal to believe her innocence in "The Six Napoleons".
- Distant Finale: "His Last Bow".
- End of an Age: The central theme of the last season: "The Case-Book of Sherlock Holmes". Queen Victoria has passed and now King Edward VII is on the throne and with him comes rapid modernization and Holmes increasingly begins to feel he's the relic of a bygone age whose pass his prime and decides to retire.
- Grand Finale: "The Retired Colourman" has been reworked as the finale for the Doyle canon with Mycroft and Lestrade making cameos — Lestrade about to retire and Inspector Gregson having done it long ago; and Holmes deciding to retire after letting Watson alone with the criminal, seeing it as a sign he's slipping up as he gets older by putting the good doctor in danger; there's also a newer detective on the scene — Mr. Barker. After the case is solved, Holmes leaves 221B for the Sussex Downs and his beloved bees.
- I Should Have Been Better: Holmes' reasoning for his retirement; his skills are deteriorating with age.
- It's All My Fault: Holmes blames himself for the Downer Ending of "The Valley of Fear", only for Watson to point out if Moriarty is as good as Holmes' said there's nothing that could've been done.
- Large Ham: A necessity given the medium, but Clive Merrison makes Jeremy Brett seem tame!
- Mandatory Unretirement: In "His Last Bow", Holmes is content with retirement and is furious when Mycroft tells his superiors where his cottage is and they try to convince him to uncover a Germany spy ring — it takes a lot of persuading but Holmes eventually relents. And after that it's back to the Downs and his bees.
- Named by the Adaptation: In this version, Inspector G. Lestrade becomes Inspector Giles Lestrade.
- Narrator All Along: The flashbacks of the "The Valley of Fear" are narrated by some mysterious person. The ending reveals he's in fact Professor James Moriarty himself reading Douglas' manuscript of his time in America.
- War Is Hell: As a veteran of the Afghan War, Watson knows this all too well. In "His Last Bow", he's disgusted by how eagerly the young are ready to go to war without knowing or thinking what it's really like.