|In the DWU|
|Main roles:||Jim Callum, Deputy Chief Caretaker|
|Notable non-DWU work:||Reilly: Ace of Spies|
Merrison has had several recurring roles on television, e.g. Reilly, Ace of Spies (as Boris the Russian), Kit Curran (as Damien Appleby) and The Borgias (as Ascanio Forza). One-off appearances include the likes of Yes, Prime Minister, Foyle's War, The Bill and Peep Show.
On radio he has played Sherlock Holmes, a role played in other media by Peter Cushing, Tom Baker, Jonathan Pryce and Nicholas Briggs. (He is said to be the the only actor to have portrayed the character in the entire Conan Doyle canon of "Sherlock Holmes" stories.)