I am running the London Marathon in April. This will be my first marathon so it's all very exciting. I really need advice on what to eat leading up to the event and during. I used to compete in middle distance but obviously my training was nowhere near as strenuous as this. I did a 10 mile yesterday and nearly collapsed even though I have run a lot further. I am thinking this could be down to diet? My legs were shaking terribly and I literally fell asleep on the ground about 5 mins after.