Milsom readily admits he was not a very good guard.

"I was never where I was supposed to be," he said. "Because I was a public servant, I had all this leave: sick leave, moving house leave. So, I was never there."

Eventually, enough was enough. He was called in to the office of the gallery director, the late Edmund Capon. Capon fired him, but at the same time gave him a rare opportunity: six months pay.

Milsom put the time the cash bought him to good use, he threw himself into his art practice. And apart from much publicised periods of incarceration, he has never stopped painting.

Last week, Milsom was announced as a finalist for both the Sulman and Archibald Prizes. He has previously won both.

However, he claims that these wins and awards always feel slightly off-target, because he is more interested in mastering the creative force behind the art, than the works themselves.

Milsom describes the process of painting as an experience closely akin to seeing an entire life flashing before ones eyes.

"You see your birth and you see your death, that's what happens during the painting process for me," he said.

"Every painting is like that for me, this flash of time ... I'm seeing this multitude of events taking place. I'm conscious of that, but I am also conscious of what I'm doing with the paint.

"Every time I start a painting, it's a different visual recollection. I try to utilise everything I have as a person, it's not about how the paint moves, that's a bi-product of the experience.

"There is a period when I start, it's all technical and rational, but to go through this door, that's where time collapses.

"It's so expansive and that's where the painting gets made, in that period.

"Now, through experience, I paint to experience that. It's still just as nerve racking, there is a lot of fear and it can be overwhelming, but now I can manipulate things in that and I can come out and re-enter it.

"I'm controlling it. Over time it has made my paintings more complex.

"My technical ability, that has stayed the same. It's walking through the door to the place where things are neither rational or irrational.

"Until I'm in that space, I can't paint. It's electrifying, high voltage and taxing and so exhausting, but also energises you and pulls you back into it.

"I've come to learn, that is the creative space."

The winner of the Archibald and Sulman Prizes will be announced on May 10.