The Telegraph has a useful overview of the supposed business case for the Olympics:
"The Government estimates that 12,000 jobs could be created in the UK in the years before the Games. But, critically, Accenture is unable to provide any concrete figures for the economic benefit, in GDP terms, of holding the Olympics in the UK. 'Any figure would be academic,' a spokesman said.
Despite the flag-waving, this lack of financial analysis makes it far harder to convince the sceptics who claim that the Olympics would be a huge drain on the public purse.
However, so far no one has found a way to come up with reliable data about whether winning the right to stage the Games provides a cost-effective way of boosting investment.
Until that happens, the business case for hosting the Olympic Games in 2012 will remain unproven."
If by some mischance the IOC likes what it sees during this week's visit, the poor British taxpayer remains on course to spend at least £5-10 billion.