Hollywood star Gerard Butler says he has been left “devastated” by the death of his “brother in arms” Darius Campbell Danesh.
In an Instagram tribute, he shared a photo of them smiling together, writing that Darius had “the heart of a lion” and was “the perfect friend”.
The Scottish singer, who was 41, was found dead at his Minnesota apartment on 11 August.
His fellow Pop Idol contestant Will Young has also paid tribute.
On Twitter, he shared a picture taken while they were on the TV talent show in 2002 and said his thoughts were with Darius’ family.
Young added: “If there was ever an example of not giving up on your dreams then Darius is top of the pile. Driven, courageous and gentle. My love goes to his family at this time x”
Campbell Danesh first rose to fame on ITV show Popstars in 2001, then the following year he finished third on Pop Idol behind Will Young and Gareth Gates.
He reached number one in the UK with his single Colourblind, then went on to become a West End star, appearing in musicals like Chicago and the Olivier Award-winning Guys and Dolls.
Colourblind has re-entered the music charts since his death, and was number two on the iTunes download chart on Friday morning.
Fellow Scot Butler paid his tribute on Instagram, writing: “I am devastated by the sudden passing of my dear friend Darius, a true brother in arms.
“My thoughts and love go to his wonderful mum and dad Avril and Booth and his two brilliant brothers Aria and Cyrus.
“To those lucky enough to have met Darius for more than a few minutes, they were deeply moved by his infectious laugh and barely containable zest for life.”
He said Campbell Danesh was always “armed with a smile”.
The Paisley-born actor added: “He was an incredible talent, a singer whose voice touched your soul and an actor with great presence.
“But, most importantly, he had the heart of a lion. It was bigger and brighter than the sun and an energy so contagious he could light up a room in seconds.”
Butler said his friend was “always constant and unwavering in his passion for life”.
“But a bigger constant was his dream to inspire others to better themselves,” he said.
“He talked the talk but boy, did he walk the walk.
“He had such purity of thought, a deep wisdom and constant gratitude for people, for life, a compassion towards all.”
Butler added that Campbell Danesh’s commitment to his family, friends and the world made him “the perfect friend”.
Ariel Vroman, director of The Iceman, replied to the post, saying: “Amazing words my brother – we will miss Darius a lot.”