Director Gordon Morrison said the gallery had decided to purchase The ersatz by Marcus Wills, a nearly three-metre piece that depicts the award-winning dancer James Batchelor.

He said an anonymous donor had also purchased the winning portrait of Barry Humphries, Barry by Louise Hearman.

The two pieces, which have been sold for undisclosed sums due to strict commercial-in-confidence rules, will be placed in the gallery’s permanent contemporary collection, the Williamson Gallery, once the exhibition finishes its tour next August.

Mr Morrison said The ersatz was a natural choice for a permanent addition to the gallery.

“I guess when we were unpacking the exhibition, to my mind, that was the work that I kept coming back to and I wasn’t the only person in the room who got that kind of feeling from the painting; it’s got such an amazing presence,” he said.

“With a lot of large-scale paintings, they end up being grandiose and overblown statements, but in the case of that painting, the scale goes with the composition, it goes with the subject.

“You get this amazing feeling when you’re in the presence of this work, it’s like going into the British Museum or the Cairo museum and being in the presence of an ancient sculpture. Someone has rendered a human figure so well and it does something, it’s quite special.”

Mr Morrison said the painting would have a “fairly commanding position” in the Williamson Gallery, but also wanted to see what it looked like hung next to Ajax and Cassandra by Solomon J Solomon, which the gallery purchased in 1887.

“At some point I want to bring those two together to see how monumental semi-naked figures...speak to each other across the room.”

Mr Morrison said he had not expected the anonymous donor to purchase Barry for the gallery.

“All I can say is that person is a very, very keen supporter of visual arts, that person is a collector in their own right and it almost knocked my socks off when I was told it was going to happen,” he said.

“That kind of generosity doesn’t happen every day.

“It was a worthy winner of the prize, it does all the things that one would hope for in a Louise Hearman work where you’ve got this play of light against shadow, and there’s the extra dimension, the extra loaded meaning. An actor, we talk about them being in the limelight and that’s exactly what Louise Hearman, the artist, has subjected Barry Humphries to in that painting.”