Im doing 2 x 20 milers. Its my 3rd marathon but 1st one was ruined as cousin was so slow and collapsed halfway ended up in hospital. 2nd was new york last eyar and it was awful, jet lag, ill, walked 10 miles day before.
Im fitter now then those 2 and will be a stone lighter too.
Im going to to a 20 mile run 3 weeks before, maybe push to 22 if I can.