American economist Dan Johnson has developed a special model for predicting Olympic winners based on the populations of countries and other factors. Over the years his predictions have been 93 per cent accurate, so you may like to use them as a starting point before placing your bet.

His forecast for 2012 is quite believable, if not very exciting - he thinks the overall winner will be the US, with China in second place and Russia in third. The UK he puts in fourth - possibly helped by being the host nation, which is usually supposed to give an edge.

This is the same order as the 2008 Olympics, but of course that's very often how it works - the bigger countries do tend to come top. That doesn't mean there will be no surprises, of course - especially if you look at individual winners, which are much harder to predict. You can see a list of promising individual contenders here.