A video art installation by the artist Bill Viola has been unveiled in St Paul's. The work, Martyrs, features four people undergoing suffering through water, earth, air, and fire, and is on display behind the high altar.

Canon Mark Oakley said that the piece, although contemporary and "risky", fitted St Paul's well. "Film is exceptionally powerful," he said. "I think this is a spiritual piece of work which asks urgent questions: 'Who have I become?' and 'Is there anything worth dying for?'"

On four screens, each figure is embroiled in water, fire, wind, or earth, and yet remains unchanged. The artist said that Martyrs and its companion piece, Mary, to be installed next year, should inspire contemplation and devotion.

Canon Oakley also said: "It shows the fragility of the human being and the resilience and dignity in the face of that which would overcome the good. Art will always divide people, but this piece of work is clearly based on Christian iconography. This is not a radical rupture into the cathedral - Mary and the martyrs have always been the saints remembered in that part of the cathedral."