Geoffrey Rush with the portrait of Billie Brown, which he has loaned to the Bille Brown Studio in South Brisbane.

Geoffrey Rush with the portrait of Billie Brown, which he has loaned to the Bille Brown Studio in South Brisbane. Photo: Natalie Bochenski

Actor Geoffrey Rush has delivered a heartfelt tribute to his longtime friend, playwright and actor Bille Brown.

Brown died of bowel cancer last month, aged 61.

On Monday Rush unveiled a portrait of the thespian in the foyer of the Bille Brown studio at South Brisbane, on an extended loan.

The Sydney Theatre Company commissioned Ben Quilty to paint the bold portrait last year.

It was the poster for The Histrionic, Brown's final stage performance.

Rush said he was "amazed the work was floating about in the marketplace", after he was alerted to its presence at the Jan Murphy Gallery in Fortitude Valley.

Rush was in Brisbane at the time, visiting Brown in hospital for his 61st birthday.

"In those bittersweet penultimate days, I told him I wanted this painting to be a gesture of remembrance of our shared lives," he told the crowd of family, friends and colleagues at Monday's dedication.

"He clutched my hands and from his bright shiny eyes tears cascaded down his cheeks. I said it's time to get it off the side of a bus, and place it in its proper home, here at the studio."

Artist Ben Quilty said he captured the image in one sitting in his country studio last year.

"I knew that night that it worked, I knew that there was just something very alive about the subject, and I was lucky enough to get it down that night, like recording a moment," said the Archibald prizewinner.

Quilty said Brown had no problem taking his clothes off for the sitting.

"I'd read the play and it was so much about someone exposing themselves, falling into madness, and opening yourself up ... so I wanted him to be naked, and instantly his clothes dropped and he was reclining in this amazing pose," said Quilty.

"It just happened very naturally ... [although] we drank quite a bit of red wine beforehand."

Quilty said Brown was brilliant at conveying life and energy, without moving a muscle.

"He started crying at one point and said "You are the Caravaggio of my night', which is the most theatrical thing I've ever heard in my studio."