ID This TV Movie (Early 70s caper flick)

I just saw a reference to the old Sammy Davis Jr/Peter Lawford movie Salt & Pepper and I misremembered it as a very different film. The one I remember was about a wealthy British aristocrat (possibly played by Peter Lawford) and his disinherited (due to primogeniture) twin brother, who tries to hit him up for some cash. The rich twin dies suddenly and the poor one scrambles to take his place. Lame hijinks ensue. I vaguely recall this playing in the timeslot reserved for NBC Sunday Mystery Movie, although it never should have. Anyone remember what this was called?

One More Time, the sequel?

That’s the one, thanks!

Screenplay by Jon Pertwee’s brother!

…or Jon Pertwee, with a fake accent and a cheap pair of glasses!