Niall Horan strips down to just his tight white boxers for unique performance of Steal My Girl in One Direction's hotel room

One Direction's first 'access all areas' movie, This Is Us, promised 'more shirtless moments than you can imagine.'

But recent behind-the-scenes footage from the band showed their cheeky antics had reached an all-time high when Niall was filmed dancing to Steal My Girl in just his boxers.

The singer, 21, showed off his abs as he delivered an impassioned performance of the new single in his hotel room alongside band member Zayn.

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Off duty: One Direction's Niall Horan strips down to his smalls for an impromptu performance of Steal My Girl in his hotel room

Niall can be seen shaking his stuff in just his underwear when the star runs into a room where his band member is recording.

He performs a twirl in his smalls before breaking into an impromptu sing off with his band mate, as they recorded the track for new album FOUR. 

Niall and the rest of the boys were caught on cameras as they prepared for their Where We Are tour and provided a unique insight into their crazy lives for an NBC TV Special. 

Niall from 1D strips down to his boxers and dances

Showing off: Niall gained a laugh as her larked about in the hotel room while the band tried to record FOUR, their fourth album

Shirtless: Niall was caught on camera as the band filmed a special NBC documentary behind the scenes of their tour

Confident: The body confident star was captured doing anything for a giggle as part of a new TV documentary

Harry, Niall, Louis, Zayn and Liam, touring South America at the time, were saving up footage for their follow up film, Where We Are, which hit screens in October.

The debut film, This Is Us, drew £40 million at the UK and US box office and topped the box office in its opening weekend.

Director Morgan Spurlock promised of the initial film: 'There are more shirtless moments than you can imagine.' 

One Direction's Niall Horan poses for a group picture with fans

Cheeky chappy: The singer, 21, who is known for his spirited nature, delivered an impassioned performance in just his tight white boxers

Making a movie: Behind the scenes footage of the band has been particularly popular with the fans, such as when they filmed their debut big screen hit This Is Us

He continued: 'We spend a lot of down time with the band, with their families and friends. We really wanted you to see what their 'normal' lives are like.'

One Direction released the DVD six days before Christmas charting at No1, much to the dismay of parents, and even aired their TV special on 23 December.

The NBC Special drew 3.1 million viewers in the US, which was closely matched by Kelly Clarkson and Michael Buble.

The boys are currently promoting their fourth album, FOUR, the recording of which featured heavily in the one-off documentary for NBC. 

On the road: One Direction filmed their NBC Christmas special while touring North America in 2014

Movie stars: 1D followed up their first movie with Where We Are which was released in cinemas in October