June Brown from Eastenders
It's always interesting with old movies to spot the actors in smaller roles who went on to become household names.
Murder By Decree has June Brown who became in national institution playing "Dot Cotton" in Eastenders. Even as someone who never watches it, I know who she is.
You'll have to look hard to spot her though; she only appears for a few seconds, in the flashbacks of Donald Sutherland's character.