Twisted from grief - as when had he ever taken something for himself beyond his freedom - he became selfish.
He wanted her. So much taken from him, it was his turn to take. He took the girl. Not against her will - but he had words to twist her will, make her come to him the way he chose. He would have her without compromise, without negotiation, without suffering through her mum's shepherd's pie.
War-damaged conscience was skating on thin ice carrying her off this way, and he felt it. He might satisfy his scruples by keeping sex out of it - let her have her boyfriends. Still he would have her as and when he chose in a way they would never. This was more important than that.
It was not until the Blitz that he began to wonder if the old muttering and shaking of heads in his father's direction had started from something like this.