A. There was, here, at that time, a kind of universal, upper-class assumption of superiority. People didn’t mind if you came to their house or you shot their pheasants, you ate their dinners or went to their daughter’s dances. But, my God, they didn’t want you to marry her. I felt it as a Catholic when I was young. One of my first girlfriends was from a fairly senior Jewish family. They were a very nice family — I’m still friendly, actually, with the girl and her brother. But her parents wanted a Jewish husband. And it’s a very strange feeling when you realize that people don’t like you because of what you are.

Q. Would Lady Cora — who we learned also has Jewish ancestry — have been able to avoid this?

A. There were Jews who came over in the 19th century, who did incredibly well and joined the upper classes. I talked, when I was doing this story, to quite a lot of Jewish historians. I have one particular friend who said that wasn’t that unusual. If you were happy for the children to be Episcopalian, then the marriage was fine. To a certain extent, that drawing-room anti-Semitism, if you can use the phrase, went on through the 1930s. But a lot of them, including relations of mine, were shocked out of it by the revelations at the end of the war [World War II]. Mind you, I would love to say to you it’s faded away. But I’m horrified by the rise of anti-Semitism that we’re witnessing today.

Q. Are you approaching your NBC drama, “The Gilded Age,” differently for an American audience?

A. I’m going to do the pilot this year. I’ve got a list of potential advisers, and I am a big, big fan of Edith Wharton and Henry James and that period of history after the Civil War — the Vanderbilts and the Whitneys and all of those people. As for adapting what I write for American audiences, American audiences have enjoyed “Downton.” I try and make TV shows that I’m going to want to watch. And when I’m reading it, I’m saying to myself: “Is this boring? Are you still enjoying this scene? Shouldn’t it be over by now?” [laughs] I can’t imagine my departing from that principle very far.

Q. Are you starting to think about how “Downton Abbey” might end?

A. It’s not really my decision. I don’t own “Downton Abbey” now. NBC Universal [which owns Carnival Films] owns “Downton Abbey.” So I could walk away, but I wouldn’t walk away. It’s too much my baby. It won’t go on forever — I’m not a believer in that. But I can’t immediately now tell you where the end will be.

Q. So the idea of continuing with these characters into post-World War II Britain ... ?

A. For me, that would be a different series. Maybe people would say, “Oh my God, that’s baby George, grown up!” But I don’t think it would be continuous, with Michelle Dockery with her hair covered with talcum powder.