Ricky - I am sure that this type of thing happens to most of us at some point oin our quest to achieve our goals. I know that I have had those kind of issues in the past. I would guess that you just ran out of gas as there was quite a few hours between eating and running and then 14 miles with no additional fuel would be a major challenge.
I have found this time that I can go upto about 15 miles without taking on board any additional food / drink (certainly in the recent weather conditions) provided that I have eaten in advance and have been keeping myself hydrated. More than that and I am just bringing a sports drink for now.
Closer to the marathon I might try some gels but have never been that keen on them.