A scene from “Unfinished Business”

Penny Knatchbull: Norton thought it was morbid to have her so close, but I wanted somewhere I could see her every day. Be near to her every day. It also means I can never leave here.

Prince Philip: Why would you want to?

Penny Knatchbull: It's not always easy.

Prince Philip: You know, one of the many, many things that attracted me to Lilibet was that the commitment would necessarily be lifelong. And to a young man who'd had such an unsettled nomadic childhood, the clarity of that permanence felt so reassuring. It still does. But it brings its problems too. Because it doesn't take into account the one thing human beings do the minute they make a commitment to a life together.

Penny Knatchbull: Which is?

Prince Philip: Grow in separate directions.