The Duchess was said to be moved by the service

The Duchess of York was meant to be visiting the firm on the day of the attack because her charity, Chances For Children, had space in the Cantor Fitzgerald offices.

Her official spokeswoman said she travelled to New York for the service and was leaving on Monday.

She signed the company's wall of remembrance and brought cards from her daughters Beatrice and Eugenie. Princess Beatrice wrote "be brave and keep your heads high".

'Be strong'

The firm's chief executive, Howard Lipnick, whose brother was among the missing in the collapse, spoke at the service.

Frank Maduro, whose brother-in-law Eric Stolman was among the missing workers, said Mr Lipnick's words had helped him to cope with his loss.

"He said we should all be strong and bond together, and that he would never forget the ones that have gone or the ones that were present with him," he said.

"They are working hard to make sure we all have physical, emotional and mental support and he gave us hope that the company would work hard to become strong again but would never forget those who died."