Russell Lynch: Is it any wonder that the summer spending boom has turned into a Fosbury flop?

George Osborne will have plenty to ponder when the Olympic caravan finally leaves town

When the greatest sporting show on Earth is finally under way after a seven-year wait, it's difficult to set aside the euphoria and take a hard-headed view of how good the Olympics will be for the British economy. But talk of deserted bars and restaurants in a central London "ghost town" gives us an early warning that the benefit of the Games (whisper it) might not be all it's cracked up to be for a troubled recovery. And after the shock 0.7 per cent contraction between April and June, we could badly do with a boost.

So what do we definitely know about the economic impact? Despite the disappointing ranks of empty seats at venues, the Office for National Statistics estimates that sales of tickets – bought last year but only counted in the official figures now – will add 0.1 percentage points to growth. So that's a good start.

But the other benefits of the London 2012 are more difficult to pin down. For every eager tourist flocking to the capital to visit the Games, another could stay at home or head somewhere else on holiday for fear of disruption, overcrowding and inflated prices. Analysts at Goldman Sachs say the extra spending could add as much as 0.4 percentage points to the economy – about £60bn – but also warn that Games tourists simply crowd out other would-be spenders. There is also the risk that Britons will stay glued to their televisions for the duration of the Games, rather than hitting the high streets to spend their hard-earned cash.

Coping with transport restrictions, such as the "ZiL" traffic lanes reserved for officials and athletes, is also an issue when London is such a key driver of the overall economy. The big property landlords who own swathes of the West End have for months been braced for transport disruption and lower visitor numbers.

Because of the extra working day, the economy is virtually guaranteed to bounce back by about 0.5 per cent in the current quarter. If the Olympics can add another 0.5 per cent to that, the prettier growth figures would certainly to help ease the immediate pressure on the Chancellor. The bigger problem for George Osborne is that the underlying economy hasn't shown any growth for two years. He has plenty to ponder when the Olympic caravan finally leaves town.