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One Direction are to release a new song called Best Song Ever.

The single appears on a full-length trailer for the boy band's 3D documentary film called This Is Us.

Super Size Me and 30 Days director Morgan Spurlock is behind the movie, which is due for release in August.

The trailer, which lasts more than three minutes, shows the group travelling around the world on tour and also features interviews with each member and their families.

Fans will see Niall Horan pouring miso soup over his rice in Japan, Zayn Malik buys a house for his mum and Harry Styles visits the bakery where he used to work.

Spurlock, 42, has been following the fivesome to events including this year's Brit Awards, where they won in the global success category.

The director called the film "an incredible opportunity and an amazing moment in time for the band" with Simon Cowell, boss of One Direction's record label Syco, describing it as an "access all areas, behind the scenes" look at the group.

One Direction is made up of Niall Horan, Zayn Malik, Liam Payne, Harry Styles, and Louis Tomlinson.

They finished third on The X Factor in 2010 and have since had three number one singles in the UK with both their albums topping the Billboard 200 chart in America.

They are on tour in North America with dates to follow in Australia and New Zealand.

One Direction announced a world stadium tour for 2014 in May with five dates in the UK.

The single Best Song Ever is available on pre-release from midnight on Wednesday.

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