One Direction celebrate their 8th anniversary this week, and former members, Louis Tomlinson, Niall Horan and Liam Payne marked the day with tweets to their fans.

Harry Styles joined in with the celebrations by tweeting this morning (July 24): "Wow, Eight years has passed. Thank you for all the love, thank you for all the support. Thank you for everything. I love you. H"

Styles has just finished a mammoth world tour during which he raised over $1.2 million for charity. He has already began work on his debut TV sit-com, 'Happy Together' based on his life. Watch the trailer below.