Hi, I'm running the Brighton Marathon in April and I'm out for 4-5 weeks after a minor operation. I had a reasonably good level of fitness before my op (I've run a previous half-marathon and did a 10 mile race just before my op in 1:33) and I was running 3 times a week. I'm now panicking a bit that I'm going to lose a lot of my fitness and not have time to train properly. I can start running again on 10th December so that will give me about 18 weeks. Are there any more experienced runners who can give me some advice, or anyone who's been in a similar position? How much is my fitness likely to decrease in 4 weeks? Any help much appreciated!