Liam Payne and Kate Cassidy planned to get married

Kate - who had been in Argentina with Liam until two days before his death - wrote on Instagram: "A few weeks ago, we sat outside on a beautiful evening manifesting our lives together.

"I keep your note close, even though you told me not to look at it. It said 'me and Kate to marry within a year/engaged and together forever 444'.

"Liam, I know we'll be together forever, but not in the way we had planned. You'll always be with me. I've gained a guardian angel."

Kate's social media post featured various photos of herself and the pop star together.

She shared: "My heart is shattered in ways I can't put into words.

"I wish you could see the huge impact you've had on the world, even as it feels so dark right now.

"You brought so much happiness and positivity to everyone - millions of fans, your family, friends, and especially me."

Kate described Liam as her "best friend" and the "kindest soul".

She said: "You are so incredibly loved. You are - because I can't say were - my best friend, the love of my life, and everyone you touched felt just as special as I did.

"Your energy was contagious, lighting up every room you walked into.

"None of this feels real, and I can't wrap my head around this new reality of not having you here. I'm struggling to figure out how to live in a world without you by my side.

"Together, we got to be kids again, always finding joy in the smallest things."

"Liam, you had the kindest soul and the most fun-loving spirit. It feels like I've lost the best part of myself. I can't imagine a day without your laughter and love. You brought so much light into my life."