The Birds Nest Stadium was the focal point of the Beijing Olympics. Credit Evangaline Lee Yuk Ching.

+ The challenge of long term benefits is just that: they accrue over the long term.

Cities battle fiercely for the right to host events, whether it is the Olympic Games, football or rugby world cups, or a G20 summit. Why do they do this? And is their enthusiasm misplaced?

The physical legacy of mega events is the most obvious. Cities commonly engage in an orgy of construction – of sports facilities, housing, hotels, transport, communications infrastructure, even whole areas of the city – and this in itself is in many cases presented as justification for chasing an event.

But if a city is merely bringing forward a construction programme in order to meet the demands of a single event, then it is in danger of creating a construction cliff to fall over after the event is over. Sydney fell off that cliff after the 2000 Olympic Games and has only just found itself able to get moving again more than 10 years later. But at least Sydney created facilities that have been in continuous use after the games. Athens is the most egregious, but not the only example of cities that have built facilities with little or no post-event value. Barcelona, in contrast, successfully used the 1992 Olympic Games as an opportunity for urban renewal and London is doing the same. Of course the challenge here is to balance long term urban regeneration needs with those of the event itself.

More generally, cities look for positive economic impacts. The cost of preparing for and staging a major event can be eye-popping, but cities bank on direct and indirect economic benefits to balance the ledger. Of course, costs typically overrun and benefits generally do not meet expectations (hopes?), so this equation is a fraught one. In any event, it is often difficult to disentangle economic benefits that might derive from an event from changes in the city’s broader economic environment. Atlanta, for instance, benefitted from a broad trend of rising investment in the southern US states unrelated to its hosting of the 1996 Olympics.

Branding is key. Cities relish the chance to showcase themselves to a broad remote audience and typically invest a lot of effort in presenting themselves in a favourable light in order to attract ongoing tourism. This doesn’t always work – in the wake of a perplexing absence of a tourism bump after the 2000 Sydney Olympics, Tourism Australia developed its infamous ‘Where the Bloody Hell Are You?’ campaign, which I think did more to damage the Australian brand than help it.

There is the hoped-for benefit of rising sports participation deriving from major sporting events, but the evidence to support this occurring is thin. More broadly, major one-off events provide a focus for intense community involvement through volunteering – approximately 50,000 people volunteered for the 2000 Olympics in Sydney and they still see themselves as a cohesive group more than ten years after the event

And then there is legacy momentum – the creation of institutions and processes and activity that continue to bear fruit long after the event has moved on. Achieving this is one of the strongest benefits of hosting a mega event. This momentum depends on the effort expended in preparing for the event and fits into a broader agenda of value for the city.

The challenge of long term benefits is just that: they accrue over the long term. And as time passes it gets more and more difficult to point to one two week extravaganza, place hand on heart and say: great things happened because of that event. So we are left with taking things on trust, just leaning back and looking through misty eyes as elite sports people do amazing things.

So, I look at London from the other side of the world and ask myself: will it be worth it? Will the temporary pain and indignity of living in a city overrun by soldiers and bristling with weapons be outweighed by the benefits after the weapons have been put away and soldiers gone home? Will the regeneration of a vast precinct in the city take hold? Will institutions and practices survive and drive better outcomes? Will the Olympics be a celebration of a great world city that primes the pump for the next era of its development?

For London’s sake I hope so.