I think from the 70s or 80s, a white, privileged Englishman murders his beautiful wife's lover and tries to pin the charge on someone else. The marriage is one of convenience, as I recall, but he suddenly gets jealous of his wife's lover and murders him. He thinks because of his "position" in society, he'll be found not guilty. Something about his family's tartan pattern found with the body eventually gives him away. The actor who played the lead looks (as I recall) kind of like Charles Gray or Gert Frobe (although Frobe was German - this actor was definitely British). I'm pretty sure it takes place in Africa (probably South Africa?).