It has been a long road to equanimity for Fellowes, who was born in Cairo, the fourth and youngest son of Peregrine, a diplomat. A recurrent bout of tuberculosis derailed his father from becoming an ambassador; he became an executive for Shell instead. “I think he had a lingering sorrow that the career he adored was taken from him,” Fellowes said. “If he had been an invalid all his life, he could have borne it, but the truth is he stayed perfectly healthy and died at 86, so it was all for nothing.”

To have a father so thwarted seems to have made his son work harder. Fellowes graduated from Ampleforth and Cambridge and ran with the upper classes, though he saw himself as something of an outsider, the “bottom of the top,” as he once put it: “I wasn’t handsome, titled or rich. I was always the man who was asked because they were short of boys or because someone had dropped out, and I think that allows you to be a sort of fly on the wall, because nobody’s paying you any attention.” He observed plenty and tried putting that knowledge to work as an actor. While a student at the Webber Douglas Academy of Dramatic Art, he earned money by writing romantic and historical fiction under pseudonyms. After graduating in 1973, he discovered that working-class actors like Albert Finney and Tom Courtenay were the ones getting serious, career-making roles in new plays at the National Theater. His upper-class accent and, he maintains, his conservative beliefs relegated him to West End comedies and revivals, playing butlers and lords: “There was an assumption that if you came from my background, you couldn’t have much to say.”

By 1981, Fellowes gave up on storming the National and moved to Los Angeles, where he spent two years playing minor roles — he was the chauffeur in “Rita Hayworth: The Love Goddess,” starring Lynda Carter — and finally found himself poised for his big break: replacing Hervé Villechaize on “Fantasy Island.”

“They decided that a really good idea would be to replace him with an old English butler,” Fellowes recalled. “So they looked around, it was in pilot season, and discovered there were two pilots with old English butlers. And someone said, ‘Wait a minute, instead of having an old English butler, have a young English valet.’ This idea of course was greeted with shrieks of delight. So the search was on for a young English valet, and I went right up to the top meeting, and then what happened is they decided they’d do better with an old English butler. Of course, if I had known the ways of Hollywood better, I would have seen that was absolutely inevitable.

“But the Hollywood experience was very interesting for me,” he added. “I had friends there, and often they would ask me to read a script. They’d say, ‘I’ve been offered this, what do you think?’ and I got into analyzing scripts and how they work.”

When Fellowes returned to London in 1984, he was cast frequently on television. In 1989 he met Emma, and they married the following year. “One of the things that you’re not really in control of — apart from everything — is your smell,” he said. “Different things in your life make you smell different, and a combination of coming back from Hollywood with a much more directed sense of what I wanted and then meeting Emma and being, I think, a less anxious person in consequence, was not coincidentally when I started to get more interesting work.” He spent nearly five seasons on a sitcom, “The Monarch of the Glen,” and had some small film roles. He also wrote successful adaptations of “Little Lord Fauntleroy” and “The Prince and the Pauper” for the BBC. Then came “Gosford Park.” His anxiety went from “will I ever make it?” to “might I lose everything?”

“I think I’m more fearful of the future now,” he said, sipping his tea. “I always feel that there’s some giant hand about to lean in and snatch it all away from me, saying, ‘That wasn’t meant for you.’ Emma has this completely different quality of living in the present. It’s just been very helpful to me to live with someone who doesn’t think, Oh, my God, what if it all stops tomorrow? Of course it’s absurd to live your life dreading some unspecified disaster.”