One family firm supplies seating for most of the West End’s theaters, from flexible new spaces to Victorian treasures. Its chief designer reveals some tricks and traps of the trade.LONDON — Earlier this month, during the first performance at the West End’s newest theater, @sohoplace, the audience repeatedly cheered the actors performing “Marvellous,” a comedy about a British eccentric. At one point, several hundred theatergoers even applauded a technician who came on to clean the floor.But there was one person key to the evening whom no one cheered, whooped or even politely clapped. And Andrew Simpson, the designer of the theater’s seats, was happier that way.“If a seat’s good, you don’t notice it,” he said. “You only notice it when it’s bad.” In the world of theater seating, he added, “No news is good news.”Simpson, 62, is in a position to know. He is the lead designer at Kirwin & Simpson, a family firm his grandfather founded that started out patching upholstery in a local movie house during World War II and now supplies the seats for most West End theaters. (It works with some in New York, too, including the Hudson Theater and St. Ann’s Warehouse.)Andrew Simpson, Kirwin & Simpson’s lead designer (and the grandson of the company’s founder) at the firm’s headquarters in Grays, England.Tom Jamieson for The New York TimesThe West End is challenging territory for a seating designer. Many of the London theaters Simpson caters for are Victorian jewel-boxes: tight, ornate spaces built with more attention to gradations of social class than to comfort.Originally, according to David Wilmore of Theatresearch, a company that restores historic theaters in Britain, they would have had a few front rows of luxurious armchairs — known as fauteuils — for their wealthiest patrons. Everyone else sat on wooden benches. When middle-class visitors were finally accorded seats, Wilmore said, theaters preserved their old sightlines by forcing the sitters bolt upright — “part of that Victorian strictness in all areas: ‘You jolly well better sit up and listen!’”That won’t do for seats that now often cost hundreds of dollars to occupy.A recent tour of Kirwin & Simpson’s works in Grays, a working-class town east of London, included a room filled with rolls of multicolored cloth and a shed where five men were busy screwing, stapling and gluing sleek maroon seats for the forthcoming Ronald O. Perelman Performing Arts Center in New York. One warehouse is filled with emergency replacements, so that if a seat rips at, say, the Victoria Palace Theater — the London home of “Hamilton” — a new, perfectly matching one can be installed within hours.Each theater needs many types of seats. The new, 602-capacity @sohoplace has 12 types, according to Simpson, all removable to allow different styles of staging, but some tricky older spaces require far more.A seat that Kirwin & Simpson designed for @sohoplace, a West End theater that opened this month.Tom Jamieson for The New York TimesThere are high chairs with built-in footrests, to give a clear view from the back of Victorian balconies where front-row patrons would once have sat directly on a low step. There are chairs with wide backs, but smaller seats, designed to fit perfectly into tight curves, and others with hinged armrests that can be raised so wheelchair users to slip into them. And there may be any number of things in between. Andrew Lloyd Webber’s Theater Royal, Drury Lane, has over 160 different designs, with widths and angles tweaked to ensure the best view.The seats themselves have become less cluttered over time, losing accessories like ashtrays and wire cages for men to store their top hats. But in the most cramped spaces, Simpson still sometimes employs an illusion. Short armrests make a narrow aisle feel wider, he said, because visitors don’t have to squeeze past them to get to their places, and they are then less inclined to start thinking about how little legroom they have. “It’s all psychology,” he added.It similarly helped if the show was a hit. “If the stuff onstage is really good,” he said, “then people don’t mind what they’re sitting on. If it’s anything less than that, then the surroundings come into focus, shall we say.”The Sondheim Theater in London, which has a capacity of more than 1,000. The seats are by Kirwin & Simpson.Tom Jamieson for The New York TimesInside the Kirwin & Simpson workshop.Tom Jamieson for The New York TimesEven with the good will of a good show, it can be tough to accommodate theatergoers of varying shapes, sizes and tastes. Nica Burns, the chief executive of Nimax Theaters, the company behind @sohoplace, said she wanted the seats in all her venues to be comfortable for short people like her (she’s 5 foot 2 inches), who don’t want their feet to dangle in midair, and for tall people like her 6 foot 3 inch husband. While the theater was being designed, she kept two Kirwin & Simpson seats in her office and asked visitors try them. But, she said, “you’ll never find a seat that suits everybody.”One demand that Simpson hears increasingly is for wider seats. Last year, Sofie Hagen, a popular comedian, began a campaign on Twitter, urging theaters to publish details of seat widths on their websites, to help larger people like her decide if they wanted to attend. “The amount of times I’ve gone to see a musical only to be in constant, excruciating pain,” Hagen wrote. “Once I had to leave before the show even started because the seat was too narrow.”Hagen said in a telephone interview that every venue on her current British tour had agreed to display details of the width of their seats and she hoped more would follow. “If theaters had signs up saying ‘Fat people are not welcome,’ people would be like, ‘What?’,” she said, “but that’s subliminally the message we’re being told.”At @sohoplace, some dozen seats at the orchestra level and balcony discreetly offer an extra three inches of width, on top of the standard 20 or so. Simpson, the designer, said that during a test event he had happily shared one with his 27-year-old son.For some, however, a big seat might be a little too much comfort. Seats that leave theatergoers “practically rubbing shoulders with one another” make for more of a communal experience, Wilmore, the theater restorer, said.An original cast-iron row end from the Victoria Palace Theater, in Kirwin & Simpson’s workshop.Tom Jamieson for The New York TimesMichael Billington, who resigned in 2019 after nearly 50 years as The Guardian’s chief theater critic, said he felt “a degree of austerity” helped keep audiences awake. For example, Shakespeare’s Globe in London has both Elizabethan-style standing space and backless wooden benches: Billington described those benches as “a form of terror,” but added that he certainly paid attention whenever he sat on one.The new seats at @sohoplace drew typically mixed reviews from some of their first paying users. In interviews with a dozen audience members at the recent “Marvellous” performance, seven were glowing. John Yee, 22, visiting from Canada and sitting in the balcony, said they were “comfy as hell.”Josh Townsend, who had a spot in the orchestra level, said he was 6 foot 2 and often struggled with seats that lacked legroom, yet @sohoplace’s were “really good.” The week before, he had watched “Dear Evan Hansen” in London’s Noël Coward Theater — whose seats are also by Kirwin & Simpson — and his legs were jammed against the seat in front. This was a huge improvement, he said.But though she had loved the show, Ayesha Girach, 26, a doctor, said the seats were so hard they were “probably the most uncomfortable” she had ever sat in. She then praised those at the Gillian Lynne Theater, just a few blocks away, where she’d recently seen “The Lion, the Witch and the Wardrobe.” “Those were really comfy,” she said. They were Kirwin & Simpson seats, too. More