Fans gather in London for One Direction movie premiere

Thousands of One Direction fans have gathered in London's Leicester Square, where the boy band's first feature film is getting its world premiere on Tuesday.

Some slept in the square overnight to stake out a spot near the red carpet. According to the BBC, the first fan to line up arrived at 9 a.m. on Sunday, a full three days early.

"One Direction: This Is Us," a 3D documentary by "Super Size Me" director Morgan Spurlock, is a backstage look at the band, which was formed on Simon Cowell's TV talent show "The X Factor" in 2010.

The five-piece group has gone on to top charts around the world and has amassed a die-hard army of fans, known as Directioners.

Band member Liam Payne said the movie was intended partly as a thank-you to the fans.

"One Direction: This Is Us" opens in Britain Aug. 29 and in the United States Aug. 30.