I have run it twice, and recce'd the route many times. Finding the top of Great End can be tricky in mist, and even in good visibility, route finding from Slight Side to Red Tarn, and then from the top of Blisco to the finish, can be challenging. Even if navigation is not a problem, the second last ascent from the River Esk is never ending, and amazingly steep if you go straight up. Good luck.