Louis Tomlinson has described Liam Payne's death as "unjust and frustrating"

Speaking to Rolling Stone UK magazine, Louis said: "It was really uncomfortable, actually, the 15th anniversary, because the [collective] feeling to celebrate is as important, if not more important than ever, on behalf of Liam."

Louis - who was put together in 1D with Liam, Harry Styles, Niall Horan and Zayn Malik on The X Factor UK - admitted marking the band's formation in the past made him feel "sick of nostalgia", but doing so earlier this year "brought up those feelings" he's been dealing with since his friend's death.

He added: "You know, there's still a level in my head [where it feels] unjust and frustrating that he's not with us anymore.

"So, it just brought up those feelings, although I'm still living with them anyway."

Louis also explained how Liam's death hit him harder because he'd "never lost a friend", despite dealing with grief in the past.

He said: "It was really, really, impossibly difficult for me to deal with losing Liam.

"Naively, I thought that because at this point, I'm relatively well versed in grief for my age, that it might soften the blow.

"[That was] super-naive. It's very different. I've never lost a friend before."

Liam has also taken the time to dispel some misconceptions about his friend, insisting "anything that he got wrong in life" was "only through miscommunication" rather than "malice".

He said: "He was just a very misunderstood person, I think, from a public perspective.

"If there is ever any judgment on his character, I think nine times out of 10, you can reflect on that, and the reflection is that he was someone who just wanted to be liked."