Kind Hearts and Coronets is a 1949 Ealing Studios black comedy starring Alec Guinness as each one of the family members who must be bumped off before our protagonist can inherit the Dukedom. I bought it for The Husband as part of this set. It's on Time's list of 100 best films. It's 6th on the BFI list of top 100 British films.
Roger Ebert has it on his list of great movies. FilmReference.com says, "Kind Hearts is very funny, wickedly subversive, and probably the finest black comedy the British cinema has every produced." Slant Magazine calls it "an interesting dissection of the pathologies of the British class system."