Maybe bidding to host the Games was a little rash, but all we can do now is stop penny-pinching and give it our best shot

Oh dear. No sooner have inhabitants of the Big Smoke got their adrenaline running with Team GB's superb performance in Beijing, than the culture secretary puts a dampener on it.

Tessa Jowell confirmed earlier this week that she had hired big-four accountant KPMG to review three London 2012 venues, seeing if the shooting, equestrian and basketball stadiums will provide value for money. One of the key tests is “legacy”, an increasingly ugly, undefined word in the world of London 2012.

These Games aren't just about regeneration and - yuk - legacy. They are a promise to Londoners of a once-in-two-lifetimes experience.

Jowell says it is unlikely that the venues will be scrapped. This is probably correct - presumably the International Olympic Committee will be keen that the guaranteed new venues are built.

This is not the point. Londoners are getting less and less of what they were promised from these Games. Presumably there will be more “value engineering” - project management speak for cutting down the costs by providing an inferior product. That is not entirely fair, as the rising costs of the Olympic Stadium are being offset by savings on items like ordering materials early, and therefore at cheaper cost. But who really thinks that the once mesmerising Aquatic Centre will be anything but a crushing disappointment?

The original cost has long since vanished. But, with just four years to go and most venues fairly solidly costed, London is simply not going to hit £20bn.

I am moving to the view that we should start ignoring cost. These Games aren't just about regeneration and - yuk - legacy. They are a promise to Londoners to provide a once-in-two-lifetimes experience. We're at £9.3bn now. The original cost has long since vanished. But, with just four years to go and most venues fairly solidly costed, London is simply not going to hit £20bn, the figure with which former Olympic Delivery Authority chairman Jack Lemley once scaremongered.

This is not something we can give up. This is unlikely to be something we can deliver for our latest budget. Equally, this is something that will not need billions upon billions more quid thrown at it.

But this is something that we are now obliged to create to the best of our collective abilities. Should we have bid for the Olympics? In my view, probably not. But it's too late; London has made commitments to its people and to the world. Let's stop whinging, and get building the best Games that we possibly can. And that means you too, Tessa.