It's going to be a warm Marathon - the Met Office is predicting temperatures of around 20°C, roughly the same as the 'heatwave' race of 2007 that caused 73 participants to land in hospital. If you're running take extra care to stay hydrated, and organisers say there'll be showers along the course for you to run under and cool down. Of course for anyone watching it'll be a grand day out, and we again point out Fancyapint's recommendations of where to watch the event with a refreshing glass of something chilled in your hand.
If you're watching near the start, keep your eyes peeled for the Red Arrows pilots - they plan to start running in the famous 'diamond' formation (but who knows how they'll finish). Also spare a thought for PC Nicholas Wharton, who was killed by a falling tree branch while training for the race.