A government report examining the Games has suggested that their economic benefits are already being felt.
The Olympics helped companies secure contracts and agreements around the world, with examples cited like deals on oil drilling in Brazil, or nuclear power in Jordan.
The £9.9bn already raised in the year since the Games could increase to as much as £41bn by 2020, meaning a substantial return on the original outlay of around £11bn to stage the event.
Prime Minister David Cameron said: "This £9.9bn boost to the UK economy is a reminder to the world that, if you want the best, if you want professionalism, if you want jobs done on time and on budget then you should think British.
"With companies across the country we are harnessing the Olympic momentum and delivering the lasting business legacy of the Games that will help make Britain a winner in the global race.
"But that's not where the good news ends. The Games are also delivering a strong social legacy.
"Last summer, Games Makers changed the way Britain views volunteering. Since then, thousands of people have been inspired to get involved with their local sports clubs."
A poll to establish the sporting legacy of the Olympics suggested that participation in sport had not risen as forecast, despite 52% agreeing with the basic premise that the Games had 'inspired a generation'.
In fact 80 per cent of those asked said they had not been prompted to play more sport as a result of London 2012, while just 6 per cent of volunteers had give more time to volunteering in sport since last summer.
However the responses from younger people were more encouraging, with 20 per cent of 16-to-18-year-olds in the poll, conducted by Sky News, saying they had tried a new sport, and 21 per cent spending more time volunteering.
"I think in large part we have inspired," Lord Coe said.
"Look at waiting lists in sports clubs, they are both optimistic and challenging, but I think there are more people playing sport, and a good chunk of them are young people."
- Sports & Recreation
- Prime Minister David Cameron