One Direction celebrates number one and Niall’s birthday with a FOOD FIGHT!

One Direction go crazy for a food fight / Rex

Those One Direction boys had a blast at G-A-Y on Saturday night with a double celebration: Niall's birthday AND their first ever number one *woop*

One Direction's debut single 'What Makes You Beautiful' went to the top of the charts yesterday.

Harry Styles, Zayn Malik, Liam Payne, Niall Horan and Louis Tomlinson got the party started early on Saturday during their performance at London's Heaven.

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They were clearly over-excited when the club owner brought out two cakes to celebrate their number one and Niall's 18th, as the jovial mood got the better of them and they started a food fight!

Zayn and Niall got their hands dirty / Rex

The lads chucked great chunks of cake into the crowd, and also splatted each other in the face.

Wonder what their parents said when they turned up with icing-covered clothes? *sniggers*

Harry couldn't contain his glee when he saw Niall smash Louis in the face with the cake. Check out that cheeky grin!

We're not surprised they were in such a good mood: they've got the fastest-selling number one of the year. Pretty amazing work for a debut single, right? Congrats lads!

Ka-boom! / Rex

One Direction celebrated their number one at G-A-Y / Rex

Niall's CUTE birthday cake / Rex

The lads were also given a cake to celebrate their number one / Rex