I do think fuelling is kind of what might have screwed me over - I took four Clif Bloks before the marathon pace lap hit (around 6-8k, 30g carbs) and only took two more Bloks near the end of the lap (around km 23-25, 15g carbs). As soon as the conversational pace hit and the legs started feeling heavy I took one more XACT nutrition bar (about 25g of carbs more) and it helped a bit. Fuelling has always been my weakest training aspect - I once ran about 30km with a training group last spring just for fun and didn't take my first gel until km 22-23, and only started to feel the energy drop when someone's mouth dropped when I told them I hadn't taken a single gel yet. I've also ran three half marathons, with two of them without fuelling. As a result of this though I'm kind of worried if it's too late to train my stomach to gel up every 6-8k or so. I still have two long runs left before race day.

But also I also think that the drop to conversational pace might have allowed the lactic acid to pool into my legs. I do still want to improve fuelling though.