I also ran my first marathon in Barcelona this year but despite following a beginners marathon training plan with quite a few long runs I fell to pieces at 20 mile. I think if I'd set myself a more challenging target 3:45 rather than trying to break 4hrs I'd of come home quicker (I sneaked in at 3:56.57). Got to say how much I loved the event and am now searching for some other European city marathons later this year, if anyone has any suggestions.