When Downton Abbey premieres its anxiously anticipated fifth season on Sunday, Jan. 4, at 9:00 p.m. on UNC-TV, fans will revel in the lives and loves of the Earl of Grantham and his extended family—and the de facto family of servants with whom their lives are closely intertwined. But an important part of the show’s appeal is its meticulous attention to historical detail. For that, you can thank not just the pen of series creator Julian Fellowes, but also the strict yet kind supervision of historical advisor Alastair Bruce, OBE, Queen’s Herald, Territorial Army Colonel and Equerry to Prince Edward.

Bruce has been touring stateside to promote the new season as well as a documentary about his tenure as Downton historical advisor, which will air immediately following the Season 5 premiere. I asked him how he analyzed the appeal of the show, which might have been relished by specialist audiences only, but is instead watched in 200 countries by an estimated 120 million viewers.

He thinks the appeal has several parts. Many people with European backgrounds are descended from someone who either lived in a grand house or, more likely, served below stairs. And in a “free and open society,” we live in a culture without much structure. Although the stratification depicted at Downton is intrinsically unfair, “everyone had a place and felt that they were contributing to the great scheme of things,” Bruce says.

“People long for the strong bonds of courtesy that feed through it all,” he continues. “You were respected, regardless of your place. And although human beings will always be sinners, there was a clear idea of what was right and what was wrong. If you wanted to have an affair, you knew it was wrong; the social contracts were absolutely clear.”

When the series first appeared, I assumed that the appeal was largely for Americans, who sometimes seem to long for a hereditary aristocracy to solve troublesome leadership vacuums. But the show was strongly popular in the UK from the first episode. Bruce says that for the British, now is a time when they can embrace their own national history in a time of renewal.

In 1832, the First Reform Act initiated electoral reforms in Britain, which continued as class boundaries eroded further during the conflagration of the Great War of 1914–’18—one reason why Downton Abbey is set in this time period.

“For a long time, particularly in the 1970s, ’80s and ’90s, British films and television were extremely uncomfortable with an aristocratic past, showing their members as stupid or bad, upper class twits and malevolent villains,” Bruce says. “But there has been an evolution in Britain. Since Tony Blair abolished hereditary peerages, so even members who had traditionally inherited a seat had to be elected by their constituencies, British society has been evolving so as not to be offended by their past.” Instead, they embrace it in all its splendor, as it appears in Downton Abbey.

One aspect of the show that puzzles some viewers is the extraordinary closeness of the upstairs and downstairs people. After all, you have another person dressing you and coming into the bedroom when you are in bed with your spouse. Bruce says that that a class structure in which everyone clearly knows their place facilitates the relationship of the Earl of Grantham and his valet, who served closely with him during the Second Boer War. Although they would not dream of socializing with one another, in the privileged space of their personal relationship, a strong bond is formed.

Bruce is a stickler for minute historical details, from dress to manners, dining to driving. His one regret has to do with the character played by Shirley MacLaine, the Earl’s wife’s nouveau riche American mother. “I let her down by not persevering in helping her to temper her brilliant performance,” he says. Because many Americans who suddenly became rich were self-conscious about appearing unpolished, they were “almost more perfect in manner than the British.” There would not have been a hint of her working class origins.

I suggested that part of the show’s appeal was how it deals with contemporary issues in a historical setting—particularly the gay footman, Thomas, and the African-American bandleader who made a brief appearance as a romantic interest for saucy Lady Rose. “We can never escape from the environment in which we live,” Bruce says. “It has to tell a story in the present. It is a great sadness to me that Thomas hasn’t had a romantic relationship as other characters have. Many footmen were gay. If you had five sons, and one of them was attractive and tall, you would have taken him up to the big house to be a footman. It may be too much of a generalization, but a footman had to have a great sense of self, be impeccably turned out and be brilliant at it, because his good appearance reflected on the house. Thomas would have found soul-mates.”

Bruce does not anticipate this storyline soon, though. “Some parts of society [today] are more generous,” he says, “and others more intolerant in reaction.”

What kinds of incongruities bother him in other period pieces? “What really annoys me are incorrect medal ribbons,” he replies. “Someone in the armed forces can identify everything about the person they’re talking to. You can see if someone is brave, and if they have a good conduct medal. Anyone who had been in the military for a long time without one would be suspect. In one scene, a person appeared without his World War I medals. I insisted that extras appeared in the scene with the correct medals. It’s not hard to do it correctly, you can find it on Wikipedia. Still, you see productions in which ribbons are worn upside down. I vilify productions fearful of doing it right.”

But Downton Abbey doesn’t hesitate to call Bruce to confer on the tiniest details. Individuals are addressed correctly, by their station, not their first names, which would have been shocking to the Edwardians. Swearing is taboo. Posture is important, as is the way one behaves at a meal (no leaning on the table, please). No profligate touching, either. “We shake hands and kiss because we have antibiotics,” Bruce says.

One extraordinary aspect of the show is the attention paid to the costumes, which have evolved from Edwardian elegance to the more revealing styles of the 1920s—with more flappers to come, I suspect. The detailed, scrupulously correct garments (and undergarments) vividly create character. An exhibition of Downton Abbey costumes, which spent the summer at Winterthur in Wilmington, Delaware, is coming to Biltmore House in Asheville from February 5–May 25.

As at Winterthur, Biltmore will contrast the daily life of grand houses in England and America. The exhibit reveals that the show is visually accurate because designer Caroline McCall has repurposed unique, fragile vintage pieces in new gowns that can withstand the rigors of filming. Bruce says that the costume department works hard “sewing beads on as they fall off” fragments of antique beaded dresses.

Would Bruce like to have lived in a different historical period? Emphatically not. He sees the role of a historian as being to “challenge people to examine the past and be kinder to each other,” especially younger audiences, whom he wishes would be more engaged with history.

As such, he cares deeply about every detail. After all, it is his hands we see in the opening credits, using a ruler to align place settings at the table. As for quibbles over a bit of a language snafu here and there? Bruce is constantly on the alert, rebuking “OK” and other modern phrases. He says, “If you hear a word or phrase on the show, Julian [Fellowes] has a source for it.” But Bruce embraces the attacks of fellow nitpickers. It means people are enjoying the story, so he just “gets the pen and paper out to crack on.”