Wallis appeared in a number of television programmes including
The Avengers (one episode in both 1966 and 1967),
Chelmsford 123,
Doctor at Large (1971),
ITV's production of
The Secret Diary of Adrian Mole, the BBC's adaptation of
John Masefield's book
The Box of Delights (1984), the first series of
Blackadder (drunken knight),
Blackadder II (Ploppy the Gaoler),
Blackadder Goes Forth (Agent Brigadier Smith),
Juliet Bravo,
Just Good Friends (A. J. Styles)
Yes, Prime Minister, and
The Beiderbecke Tapes (1987), in which he played a beleaguered Amsterdam hotelier. (1993) Wallis played the disgruntled scientist who kills his boss in Poirot (The Underdog).One longstanding role was that of the hard-drinking Nick McKenzie in the BBC drama
Dangerfield, from 1995 until 1998. He appeared as Gestapo-man Werner Beck in award-winning
War and Remembrance (1988). He also appeared briefly in the first episode of
ITV's
Midsomer Murders, apparently driving a
Morgan sports car. In fact this was pushed by other cast members, as he did not hold a driving licence. He appeared in
Not Only... But Also with Peter Cook and
Dudley Moore, alongside comic actors
John Wells and
Joe Melia, singing the
absurdist comic song "Alan a' Dale". He appeared in the original London cast of the unsuccessful
Andrew Lloyd Webber/
Alan Ayckbourn musical
Jeeves in 1975. He presented and narrated a semi-dramatised documentary titled
A Pleasant Terror on the life and works of
M. R. James, broadcast by
ITV in December 1995. Some of Wallis's most frequent appearances were on
BBC Radio 4 for
The Afternoon Play and the
Classic Serial, but he was also in the cast of the long-running sketch show
Week Ending, and in the first episode of ''
The Hitchhiker's Guide to the Galaxy'' in 1978, originating the roles of Mr. Prosser and Prostetnic Vogon Jeltz. He reprised the latter in the second episode and in one episode of the second series; however, due to unavailability, the roles of Jeltz and (briefly) Prosser were taken over by Toby Longworth. He played Winston Hayballs in
Peter Tinniswood's
Winston series. He also featured as the third party in the "...is approached by Ivor Cutler" series of short humorous pieces, including playing the Miner, the Farmer and the Sheet Metal Worker. Wallis also read audiobooks, among them unabridged productions of
Robert Harris's first two novels about the life of
Cicero,
Imperium (2006) and
Lustrum (2009). The third and final novel,
Dictator (2015) was not published until after Wallis's death. Wallis's role as narrator was taken over by
David Rintoul. He has also read several audiobooks in John Mortimer's "Rumpole of the Bailey" series. Wallis's film appearances include
The Bed Sitting Room (1969),
The Romantic Englishwoman (1975),
The Orchard End Murder (1981),
Brazil (1985),
The Whistle Blower (1986),
The Great Escape II: The Untold Story (1988),
The Fool (1990),
Splitting Heirs (1993),
Keep the Aspidistra Flying (1997) and
The Other Boleyn Girl (2008). ==Personal life==