"Payno, my beloved friend, one of my best friends, my brother, I love you, buddy. Sleep tight", writes Tomlinson.
Tomlinson was 18 years old and Liam Payne 16 years old the first time they met. Payne died on Wednesday in Buenos Aires after falling from a great height from a hotel.
"Liam was, in my opinion, the most important part of One Direction. His experience from a young age, his tone security, his stage presence, his writing was a gift" writes Tomlinson.
He also addresses his lost band colleague directly and explains that he wants to be like an older relative for Liam Payne's seven-year-old son, Bear, in the future.
"I want you to know that if Bear ever needs me, I'll be the uncle he needs in his life and tell stories about how fantastic his dad was. I wish I had the chance to say goodbye and tell you once again how much I loved you."
The other members of One Direction have also written personal posts about Payne after his death.
Liam Payne's girlfriend Kate Cassidy, who was with him in Argentina but went home earlier, has now spoken out. She writes on Instagram that "nothing in the last few days has felt real". She addresses the deceased boyfriend directly in her text:
"Liam, my angel, you are everything. I want you to know how unconditionally I loved you. I will continue to love you for the rest of my life", she writes.
