One Direction star Niall Horan was on hand to wish his bandmate Louis Tomlinson a happy birthday today (December 24).

The Yorkshire lad is celebrating his 22nd birthday and the singer has been receiving a lot of wellwishes from fans on Twitter.

Phrases including his name have been trending on the social networking website, but some fans have been left a little confused about the lack of interaction between the singers themselves.

At the time of writing, only Horan has so far tweeted Tomlison about his birthday, with the Irishman saying: "Happy birthday Tommo. Have a good one, and have a great Christmas!"

One Direction meanwhile were spotted recently filming at the top of London's Tower Bridge.

A rep has since confirmed that the shoot was indeed for their next single 'Midnight Memories'.