A large and inconvenient cat was recently let out of the Olympic bag and it is already challenging those charged with communicating the benefits of London 2012. Basically it seems that those benefits are either greatly exaggerated or non-existent.

According to a secret report leaked to The Times, the Government was aware of these conclusions well before it launched the 2012 bid. But ministers chose to shelve the 2002 report – which they themselves had commissioned. Its conclusion that economic rationale for hosting the Games was weak was set aside as an inconvenient truth. So too was the finding that the Games would do little to spawn a new era of national sporting participation.

Instead the bid was launched and won with all the razzmatazz and spiralling costs that characterised boom-time Britain. Now in days of economic bust, the report has dramatically shifted the debate.

Arguments about shifting whole rafts of the Olympic jamboree to existing arenas such as Wembley and Windsor are gaining traction. Some commentators have even suggested sending the 2012 Games back to Beijing where facilities for staging them exist.

Tessa Jowell’s renewed protestations that the enterprise represents ‘pure gold dust’ in terms of opportunity for the UK seem far-fetched.

One senior communicator involved in London 2012 told me the secret report represented the Games’ ‘weapons of mass destruction’ moment. Publicising the supposed Olympian benefits to London could become as complex as justifying war in Iraq once the original justification has been exposed as false.

Of course, London 2012 does now have the benefit of the scores of Beijing medal winners to act as compelling national ambassadors for London 2012.

And in a recession so severe that every cost seems to be measured in billions, a mere £9.3bn may appear as a mere jotting in the margin of national debt.

But the pressure is now on communicators to convey genuine prospects of a long-term return on investment from what is essentially a one-off party.

Ian Monk is founder of Ian Monk Associates and a former executive at the Daily Mail and The Sun