Thanks for the above advice. I hit up my last long run on Sunday before NYC in November taking onboard the advice given above.
Slowed the pace down to 10.40 - 11 min miles for the entirety of the run and fueled more regulary with gels at 5, 10 and 15 miles. I managed a solid and consistent 22.5 miles.
This probably shouldn't have come at a surprise, but really did, so massive thanks for your help. Was a real confidence boost to finish that run knowing I could definitely have managed the extra 4 miles.
Well I managed 4.32 for London. Not amazing but I was aiming for 4.30 so was pretty happy based on the fact that I'd followed a plan for 4.30. I'm not really built for long distance running (6ft4 and 90kg) so I kinda just see it as a mental / physical challenge, but defo want to get better.
I can run 9 - 9.30 min miles up to 15 and then it hits me like a train. Looks like a few more miles in the training sessions will help me improve so thanks again for the advice.
jeees... that would make complete sense then. Looks like I'd really underestimated the training amount needed to get where I wanted to be. Wasn't expecting any amazing times, but will have to get myself a more realistic plan for the next one.