LONDON It's hard to think of anything that Alexander McQueen and Leonardo da Vinci have in common. One made clothes out of feathers, flowers, shells and lace. The other painted intensely naturalistic religious scenes and animated portraits. But both, it seems, have the rare power to please modern crowds. Working five centuries apart, McQueen, the British fashion designer who committed suicide last year when he was 40, and Leonardo, the Renaissance inventor, scientist, draftsman and painter whose Mona Lisa and "Last Supper" are the most famous paintings in the history of art, have been the subject of two wildly popular museum shows this year, captivating the public to a degree no one anticipated. Crowds waited up to four hours to see "Alexander McQueen: Savage Beauty" until it closed in August at the Metropolitan Museum of Art in New York. An event like few others at the Met, the show was extended twice, finally staying open until midnight its last two days. By the time the show closed on Aug. 7, attendance had hit 661,509, putting it among the Met's 10 most popular shows, with McQueen right up there with Tutankhamen, the Mona Lisa and Picasso. Now lines are forming at dawn outside the National Gallery here with a tenacious public patiently hoping to get the only 500 tickets a day not sold in advance for its blockbuster exhibition "Leonardo da Vinci: Painter at the Court of Milan," which opened last month and focuses on that artist's years as court painter to Ludovico Maria Sforza, the duke of Milan, in the 1480s and 1490s. Because the works are so fragile, the show cannot travel and is on view only through Feb. 5. Museum officials say they do not have an estimate of how many people will have seen the show by the time it closes. The advance tickets, which went on sale online in May, sold out the first week the show opened, prompting box-office Web sites to start scalping 25 tickets for up to 400. Luke Syson, the exhibition's curator, said he knew the show would be a hit, but he was still amazed by the public's response. "I am struck by how we invent this figure for the 21st century," he said one recent morning, sipping a cappuccino in the National Gallery's cafeteria. "These pictures communicate something that's just out of reach. There's always more than meets the eye." On view are 7 of Leonardo's 14 extant paintings, along with works by artists in the school of Leonardo da Vinci as well as Giampietrino's reproduction of "The Last Supper," on loan from the Royal Academy in London. There are also 60 Leonardo drawings, 33 of which are from the Royal Collection. (About 10 of the show's drawings relate to the apostles depicted in "The Last Supper.") Five years in the making, the exhibition is not only a feat of scholarship but also of diplomacy, with loans from museums in St. Petersburg, Krakow, Paris, New York, Rome and Milan. Even though the exhibition has been billed as a once-in-a-lifetime event and has received rave reviews, Mr. Syson said he "wanted to make sure this wouldn't be a Marx Brothers moment where we tried to cram as many people into the show as possible." Adamant that there be crowd control so people can actually see the works properly, officials have limited the visitors admitted to 180 every half-hour, although people may stay as long as they like. That figure is under the 230-person maximum capacity of the galleries. Taking a page from the Met, the National Gallery has extended the show's hours. It now stays open until 10 p.m. on Fridays and Saturdays (it generally closes at 6 p.m.) and two more hours on Sundays, now closing at 7. For the show's last two weeks the museum will be open until 10 every night, Michelle Gonsalves, a National Gallery spokeswoman, said. And for the first time ever it will be open on New Year's Day. "We advised people to book early," Ms. Gonsalves said. And while the museum is aware of the frenzy to get the remaining tickets, it was surprised to learn that they were being scalped. She said the National Gallery's security officers could tell if tickets had been scalped, and that visitors found with such tickets would not be allowed into the show. "We can't say how we can tell, but we are doing spot checks," she explained. Despite all the madness Mr. Syson, who is leaving the National Gallery to become curator of European sculpture and decorative arts at the Met in January, has a message he hopes the exhibition is delivering: Realizing that Leonardo has recently been prized more as a scientist than as an artist, he wants the public to see how painting was actually central to the master's way of thinking. Judging by the show's popularity, that point is getting across. "I don't mean to sound like a mystical priest, but on some level these paintings communicate soul to soul," he said. "Great art does work on people in mysterious ways."