the advice I've read over the past few months suggests if you're going to be exercising for 90 minutes or longer, you'll need some more of energy bar / drink / jellybaby. There's a good piece in the Nutrition section from last month (I think). Also, the lucozade dedicated running site has advice on fueling during a run and recovery post run.
I tried dates and almonds as recommended by RW for my last LSR and didn't get on with them. The almonds dry your mouth and the dates took a lot of chewing! I've also tried jellybeans and again didn't get on with them; being very small they're very easy to drop and, in this heat, they got very sticky. They gave me a more obvious energy boost then the dates and almonds tho.