- guardian.co.uk, Thursday June 29 2000 01.47 BST
"Can you ever be over-ambitious?" Lord Foster said, when asked if he regretted the radical design of the slender "blade of light", which bounced so alarmingly under the feet of the crowds that it was closed within three days of opening. "I would rather be accused of being over-ambitious than of being lily-livered and retreating into a nostalgic past that never existed," he said.
Tony Fitzpatrick, chief engineer for Arup on the project, said: "I am embarrassed - but not ashamed of our work, or our profession." The designers insisted the problem could not have been predicted on any of the available engineering data and standards, which will now have to be rewritten.
The problem was apparently caused by the wrong kind of walking as the crowds came in unexpected numbers.
At least 150,000 made the 320-metre crossing between St Paul's cathedral and the Tate Modern in the 72 hours before the bridge was closed. When pedestrians felt the natural movement of the bridge, they fell instinctively into step, and their own movements alarmingly increased the vibration and caused the swaying.
Since then, engineers have been working around the clock. Outside firms and experts, who would normally be commercial r ivals, have been brought in to vet and check the work.
Arup expects that the solution will be to vastly increase the damping of the bridge, by building in the equivalent of car shock absorbers to prevent the build-up of vibrations. The engineers have ruled out making the bridge stiffer by adding extra piers, which would destroy the elegance of the design.
Lord Foster furiously denied the existence of a "millennium curse" which has appeared to strike both the dome and the London Eye, the big wheel which missed its New Year's Eve opening date. He said the transformation and regeneration of tracts of the capital should be seen as "the millennium blessing".
"Moving around the world as I do, I hear nothing but people being incredibly supportive. They say 'wow, there's so much happening in London, it's unbelievable'."
Lord Foster appeared shoulder to shoulder with Arup engineers yesterday, declaring: "We are all in it together; we have all in our own ways put our reputations on the line."
On June 12, the day the bridge closed, he caused great resentment by appearing to shrug off responsibility for the bridge he co-designed with Arup and the sculptor Sir Antony Caro, describing the problem as "engineering led".
But he revealed he has joined in all-night sessions in Arup's offices, trying to devise a solution that will not spoil the slender beauty of the bridge.
Teams of volunteers have spent hours waddling like ducks across the bridge, trying to recreate the bouncing and snaking movements reported by members of the public. Shakers, vibrating metal weights normally used to test the strength of football stands, are still being used to trigger and study the vibrations in the bridge, and test rigs are being designed and built to study the problem further.
Tony Fitzpatrick, chief engineer on the project, yesterday blamed "unintentional synchronisation of walking".
David Bell, chairman of the Millennium Bridge Trust, said the priority was "to give the bridge back to the people of London, for 24 hours a day, for ever".
He is already planning the third opening celebration: the bridge was opened by the Queen when only two-thirds finished in May, opened to the public with a procession and fireworks display a month later, and should reopen in the autumn. "I think we'll do something a bit different this time," said Mr Bell.
