Thousands of One Direction fans are expected at the premiere of the boyband's first film.
Some fans have slept out overnight in Leicester Square in a bid to get a prime spot ahead of the band's arrival on the red carpet. Organisers said they were setting up special areas so fans could "safely view the action from the red carpet".
They said: "Event staff on the ground, the Metropolitan Police and Westminster City Council will be working together to ensure the safety of fans, guests and staff on the day. We would like to remind fans that the red carpet is being streamed live all over the world, so they can get the best views from the comfort of their own homes."
The film, called One Direction: This Is Us, is made by Super Size Me director Morgan Spurlock and follows their life on the road during their rise to worldwide fame.
The band - Liam Payne, Harry Styles, Zayn Malik, Niall Horan and Louis Tomlinson - have already held a press conference in north London with Morgan where Liam said it had been "nerve-wracking" to make but admitted there could be a follow-up if it is a hit.
He said: "I think at the moment we just want to see how this one goes to be honest with you. It's so nerve-wracking making the film and stuff. I was thinking the other day when we sit in the premiere and everybody is actually watching it on the big screen it's going to be amazing but I don't know, maybe we'll see how this one goes, see if people like it."
Harry said the experience was "really strange" but at the same time "it kind of didn't make that much of a difference". He said: "It was kind of just getting on with the day but there was someone in your way when you tried to get out of a door."
The boyband, who were brought together on The X Factor, have topped the charts on both sides of the Atlantic, becoming the first British act to top the Billboard chart with their debut album. Louis said one advantage of making the film was it helped them remember everything that had happened to them in the last few years.
He said: "Because so much is happening to us you kind of just lose it all. It's great just to sit back and watch it back and remember and relive those moments."
Harry said the film would allow fans to learn more about them, saying: "We just want to show what we're about and with social media and stuff there's only so much you can get across in terms of your personality."Asked why there was no sex or drugs in the film, he joked: "This is a family press conference."