Last week I described "The Wall" - its biology, and what it feels like. How can we avoid it, or mitigate its effects?
Here are some points that deserve our consideration now (making due adjustment for Passover dietary customs!)
Taking on energy during the race. Some of the drink stations on the course provide "Lucozade Sport", and you should now practise drinking it (or the Tesco own-brand equivalent) before and during your training runs. One can buy "energy gels", but they seem to me to be overpriced mixtures of glucose and water. Last year I practised sucking glacier mints as I ran, and I duly put about ten sweets in my shorts pockets before the marathon. One sweet is 22 kilocalories -- that's a quarter of a mile running!
Long training runs. As I previously wrote, if, through running in company and allowing yourself a few two-minute breathers, you can manage two or three 20-miles-plus runs, they will hold you in very good stead.
If you attempt a long run but find that you "hit the Wall", then you could dress rehearse the pessimistic scenario of hitting the Wall during the race. Try switching to "purposeful walking" - walk for a minute or two to recover some energy, then alternate between brisk walking for 70 steps and jogging for 70 steps. Decide on a choreography that is manageable but still challenging, and be aware of the maths - for example, running at six miles an hour mixed with walking at four miles an hour is like running at five miles an hour. The aim should be, if worst comes to worst in the marathon, to limit the damage to your finishing time during that rough patch between 20 and 24 miles. Over the last two miles, your awareness of an end in sight, and the encouragement of the crowd, should get you back running through to the finish.