He draws his inspiration from God and Michelangelo and hopes one day to have one of his paintings hanging in the Vatican. So a commission from the Roman Catholic Church to paint an altar piece for Glasgow's St Andrew's Cathedral may be Peter Howson's first step to fulfilling his dream.

The work, an 8m by 5m painting of the martyrdom of St John Ogilvie, who was hanged at Glasgow Cross in 1615 for high treason, is the largest piece of art to be commissioned by the Church in Scotland since the Reformation. It will be completed next year and represents a huge enterprise for the controversial artist, requiring up to 300 preparatory drawings and “industrial quantities” of paint.

Ironically for a man who suffers from Asperger's Syndrome and does not like crowds, it will feature more than 600 people attending Ogilvie's execution.

Howson gave a typically idiosyncratic account of his work during a press conference at the cathedral yesterday to announce the commission. Citing the great Renaissance masters as inspirations he said that since childhood he had dreamed of completing “a major painting” for the church.

“I looked at Michelangelo and thought 'I would love to do something like that'” said Howson, who hopes one day to have a painting in the Vatican. “I'm not saying this is a stage to it, but in a way it is. If God wills it, then it is,” he added.

But if he was in love with the spirituality of the past, Howson was also appalled by the “gimmickry” of the modern scene, and lambasted the crass world of celebrity, which had created this week's most photographed objet d'art, a golden statuette of the supermodel Kate Moss, valued at £1.5million.

“Everywhere now is obsessed. The front page of a newspaper with [the statue of] Kate Moss? That is disgusting. I'm not saying it shouldn't be allowed - what's disgusting is that people think it is important. It is not important at all.

“True originality comes when you don't try to be original. The whole art world at the moment is gimmickry.

“When J.S. Bach was around he was treated like a dinosaur, as if he was old-fashioned, but he didn't care

about being ‘original' - he just wanted to write great music,” said Howson, 50.

The artist first attracted public attention when in 1993 he was chosen as official British war artist in Bosnia, an experience which deeply affected him. His dramatic, figurative work became powerfully religious after he was “born again” to Christianity in 2000, while being treated for his drug and drink addictions at Castle Craig clinic in the Borders.

However, the support of the Church represents remarkable recognition since his best known work remains a nude portrait of the pop singer, Madonna.

That painting had been a ruse, confessed Howson, to draw people into an exhibition of otherwise religious art. Nor did the controversial image hold any fears for Archbishop Mario Conti, the man behind Howson's latest commission, which will complement the refurbishment of the cathedral. “If you want to see naked figures, go to the Sistine Chapel,” recommended the archbishop.

The artist says he sees no great distinction between Catholic and Protestant, and enjoys a very personal relationship with God, attending mass with his Catholic girlfriend, and other churches as and when he feel the urge. So long as he remained “sincere and truthful” in his approach to his subject he said he could do a “good job” in representing St John Ogilvie.

“This is the martyrdom of a great man of courage. My job is to waken people through the image, people who are sleeping, who can't be bothered reading, can't be bothered looking because television and films are saturated with rubbish. They might see a painting which will move them, awaken them to this door. Once they get through the door there is a whole new world waiting,” he said.

The only difficulty which he could see ahead was the sheer volume of work on his plate.

The artist said he felt more like a football manager at a post-match press conference, rather than a spiritual guru. “It's like a game of two halves. Half of my life was a hedonistic mix. This is the second half . I'm not puritanical in any way, but I feel different. Hopefully this half will be better and I won't get sent off or anything like that.”

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