1D mania hit London, as chart-topping boyband One Direction attended the world premiere of their film, One Direction: This Is Us.

Thousands of screaming fans, some of whom had camped out overnight, greeted the award-winning group - comprising of 21-year-old Louis Tomlinson, Zayn Malik, 20, and 19-year-olds Liam Payne, Harry Styles and Niall Horan - as they arrived at the Empire cinema in London's Leicester Square.

"This is unreal," said Harry.

Niall added: "This is amazing. We're really excited to be here. We can't believe we are here."

"This is just unbelievable. The last few years have been amazing. This is what we've been dreaming of."

The 3D film, directed by Super Size Me film-maker Morgan Spurlock, is a behind-the-scenes look at the band as they embarked on their mammoth This Is Us world tour.

Simon Cowell, who signed the boys to his Syco record label, joked that he felt like a proud father.

"I feel like a father," he said, seemingly referring to reports that he is fathering a child with New York socialite Lauren Silverman.

Source: Press Release