Sunday, Bloody Sunday (1971)

Recently divorced career woman Alex Greville (Glenda Jackson) begins a romantic relationship with glamorous mod artist Bob Elkin (Murray Head), fully aware that he's also intimately involved with middle-aged doctor Daniel Hirsh (Peter Finch). For both Alex and Daniel, the younger man represents a break with their repressive pasts, and though both know that Bob is seeing both of them, neither is willing to let go of the youth and vitality he brings to their otherwise stable lives.