Willis was very good as a widower under suspicion in a "Poirot" a couple of
years ago.
The only other thing I have ever seen Alan MacNaughtan in was (briefly, as
-of all things- a choir singer ) the the video for Mike Rutherford's song
"The Living Years".
As to Richard Vernon, I understand he was in "A Hard Day's Night", which
believe it or not, I have never seen.
He also played Colonel Smithers (who, ironically, briefs James Bond and 'M')
in "Goldfinger", which I *have* seen countless times...
Best to all,
Mike V.