Waterproof jackets are one of your most important pieces of kit. Not only do they keep your head dry, you generally need to keep one handy when entering some races. But there's more to think about than just how well they keep out the rain. Do you need a coat that's well ventilated? Is this coat suitable for daily use? And what exactly is a 'smock' any way? Fortunately, Sim Benson has tested the best jackets available to make sure you stay dry on the trails.