It seemed Cantor Fitzgerald was doomed, but it has managed to rise from the ashes

They don't talk much about watching their friends die on television; they would rather confound the people who said they were finished, who said the loss of 700 colleagues and a headquarters would be more than enough to see off any company.

These are the people of Cantor Fitzgerald and their sister business eSpeed, a financial trading organisation that lost 70 per cent of its New York staff in the attack on the World Trade Centre. No other company was hit so badly, with 1,000 workers trapped on floors 101, 103, 104 and 105 of the north tower when disaster struck.

At Cantor's London headquarters near the Tower of London their colleagues watched in horror, many in tears, as it dawned on them that people they knew, cared for, spoke to every day on the telephone, had been engulfed by fire and then by the collapse of the building. It seemed the company was doomed, but it has risen from the ashes.

Yesterday, the Prince of Wales visited to offer his condolences, allowing many to stop work for the first time in two weeks to talk about their loss and their triumph. Against all the odds, the London branch of the company has re-forged links with the few remaining staff in New York and has succeeded in getting business up and running again.

"It has been a Herculean effort from the staff here," said the company's chief executive, Lee Amaitis. "They are tremendously dedicated, but the amazing thing is that when it happened, I didn't have to tell anyone what to do. They just went about doing it, working round the clock.

"It has been a tough time. I knew every one of those who died, including some friends I've known for 20 years. But the support we have had from the British public, from government and now from Prince Charles has been tremendous. It is a fantastic morale-booster."

At the last count, 12 British nationals from the company were among the missing, presumed dead. But many of the people at Cantor had worked in New York and knew the Americans who died.

"It has been a real emotional rollercoaster," said Clive Triance, managing director of operations. "I saw it happen, but I can't remember much about it. Straight away we realised all those people might not get out. It was unreal. There were a lot of tears and people here were very upset, but we also realised we had to keep going, we had a job to do, and we've done it."

Working round the clock and in shifts, some people sleeping in the office, links were restored with what remained of the Cantor staff at an emergency disaster recovery headquarters in New Jersey. "We got a whole new system up and running within 48 hours – I've only been home once in two weeks," said Dave Mudie, 24, assistant director of operations.

"We've turned a bit of a corner now and things are up and running, so I might get a day off over the weekend."

Cantor trades derivatives, treasury bonds, fixed income bonds and futures, and its spin-off, eSpeed, provides an electronic market-place where financial products can be bought and sold. On the fourth and fifth floors of their office yesterday, traders were working almost normally, though many looked tired.

Paul Norris, a stocky figure in yellow braces, said most had been working from 7am to midnight most days since the disaster. "But no one's complaining," he said. "Everyone's just doing their best to keep the company going. It has been a horrendous two weeks but we're determined to get on with it. The guys who died in New York would have wanted us to carry on."

One of the most difficult jobs has been carried out by the human resources – personnel – department. They have had to field calls from anxious relatives and, where necessary, provide counselling and other help.

"At the beginning, although it was awful, you could be positive when people called and say you were sure the missing person would be found," said Gail Cook, 27, human resources manager. "Then as the days went by, it became harder and harder to be optimistic because we all knew people were probably not going to be recovered. At that point, you got practical and offered whatever help you could. In the company, too, we've had grief counsellors, and they have been well used."

Mr Amaitis was adamant that the company would stay alive. "This company is safe and, thanks to the efforts of the people here and in New Jersey, we will carry on," he said. "It's what the guys in New York would have wanted."