Missed due to the heat!? My running partner left me at 17 miles and got a PB 3:58.40 due to shear determination, another club member got 3:55:38 and she's over 60?? Came 3rd in her age category, they both reckon they ran faster to get it over with,my body didn't agree unfortunately..will try again next year.
I suffer from exactly the same problem which occurs more often than not from 7 miles onwards. I had a pair of trainers (Nike Structure Triax) and it never happened. When they wore out I have had it non stop with a whole range of trainers including the so called upgraded Nikes. The Chiropodistlooked at my original Nikes and decided they had a really deep toe well which revised versions don't have. He stuck a 'doughtnut' shaped pad under my inner sole which sort of allowed my toes to drop through and prevent this 'Mortons toe' issue. Although not absolutely perfect it's much relieved, now only minor and definitely bearable for marathon distance. Very annoying complaint though and only get it on toes of one foot.