Two plus two normally equals four. But not when Raymond Brownell is about.

This is maths for those who get tense about trigonometry and turn to jellies at the mention of geometry.

In his designs, numerical permutations and combinations add together to make the onlooker dizzy with delight. There are no difficult sums here, simply colourful triangles and squares, teaming up to tease the brain with a flickering parade of optical illusions.

Raymond enjoys taking the mind to its limits: "It makes you humble," he says. "You realise you can't control things when the colours play tricks on you. It stops you being arrogant."

Raymond himself is a modest man but he has every reason to be proud.

Born and bought up in Tasmania, he trained in architecture and created grand buildings throughout the world, in Denmark, France, Scotland and Australia, where he helped design the Sydney Opera House.

He moved to Lewes 15 years ago and was made an MBE for the major refurbishment of the Foreign and Commonwealth offices in Whitehall, London.

These days he prefers the control painting gives him, after spending years in architecture, often working on projects that would never be built: "Painting is so satisfying because you do it yourself and you know you'll finish it," says Raymond.

He wasn't always so keen on painting. When he first encountered modern art similar to his own, in France, he was torn: "It made me curious and furious.

I wondered if it was all a con and I had to find out what was guiding these people.

That's when I started painting mathematical designs" Some modern artists still bemuse him: "I'm not one of these people who throws paint around," he says.

"I like things to be extremely precise." The result is a strict ordered art, where crisp crystalline patterns, in candy stripe colours, prance before your eyes.

The gallery is open from Tuesday to Thursday, 10am to 5pm, and Saturday 10am to 4pm. Admission is free. Paintings are available from £100. Phone 01273 681852
By Olivia Edward, features@theargus.co.uk