THERE’S only one word that comes to mind when you stand face-to-face with David Hockney’s stunning artwork. Wow!

Painted in oil on 50 separate canvasses and then pieced together, Bigger Trees Near Warter measures 15ft by 40ft and takes up the entire wall of a room at York’s Art Gallery.

Stand in front of it and the colours positively glow. The impact is almost overwhelming.

The artist himself was the only one at last night’s unveiling who did not seem overawed, contenting himself with a gentle: “It looks very good.”

But then, he has seen it before, of course: first in his studio at Bridlington, then at the Royal Academy and the Tate. “Though this is only the fourth place it has been,” he said.

Sitting in a plastic chair on the steps of the art gallery, his clothes covered in cigarette ash, he treated a small gaggle of journalists to an account of how he came to paint Bigger Trees.

It was painted to fit a wall at the Royal Academy – and he was determined it would fill the whole space, he joked. “If I hadn’t filled the whole wall, they would have squeezed something else there. I didn’t want that.”

He chose the subject after the trees caught his eye one day. “I drive around a lot. It was the trees themselves. I thought: ‘I can make something of that’.”

He painted it from life over six weeks, out in the cold of the East Yorkshire spring, on separate canvases, using a computer so he did not lose sight of the overall picture.

It was pretty cold at times, he admits. “But the people in the house (in the picture) kept bringing me out cups of tea.”

East Yorkshire continues to inspire him. Which is less than he can say for the UK’s anti-smoking policy. What do you think of York?, a hapless tourism bureau representative asked him. “I don’t come into York very often for the single reason that there is nowhere I can sit down and have a cigarette,” he said.