Well shocked by you remembering I was born in Flitwick I leapt off the sofa, leapt on to my sturdy steed and pedalled towards Pateley Bridge so as to climb Greenhow Hill. Although Simon Warren states the total length to be 3500 meters the first 1500 meters contain 300 meters of climb, starting at 16%, with another 100 meters of climb spread over 2000 meters which feel like a relative rest.
I descended to the river through Bewerly, as I have before as well as ascended this way. When I first did this I recognised the single track S hairpin bend by a farm to be the worst road surface (and when descending most frightening) I have ever ridden on in my life, and on 25mm rims. Ever. But that was then and since then it has deteriorated. Since nobody would use the route other than to visit the farm I see no reason why any highways dept. will waste money improving the surface.
All that would do would be to encourage cyclists.
Anyway 40 miles,4000 feet of climb and a maximum speed of 40 mph. Neat.