HENRY WELDON/HAVILAND MARTIN - SPOILER ALERT
SPOILER ALERT
If you have watched this great film, you will know Henry Weldon and Haviland Martin are one and the same. They are both played by Jeremy Sinden (who played Boy Mulcaster in the 1981 Brideshead Revisited).
However, the DVD lists Haviland Martin as played by Romney Marsh (in episode one credits) and Henry Weldon as played by Jeremy Sinden (in episode two credits).
Romney Marsh is a made-up name (and as unlikely as Haviland Martin - Romney Marshes is genuine and a place in Kent), I assume so alert viewers will not realise until towards the end of the film.
But IMDB lists Romney Marsh as a real actor. You can go to his site and - surprise - this little-known actor has played no other role than Haviland Martin in Have His Carcase.
Perhaps it would have been better to list the names as was done with Colin Higgins, who also played two roles in Have His Carcase. Colin Higgins: Bright/Morecambe (sorry if names are not correct - I don't have the list with me).