I think it will be more than an hour. ill get on google earth and get an exact measure. With the terrain and hills you will be hard pushed to do it in under 2 hours id guess. but its been a year since I did it so I cant right remember now
Right EDIT;
Right its 5 miles each way, so 10 miles and big ar$e hills. So ill guess ~2 hours riding so say 2.5 with stops and sorting stuff out, depending on how long people want to rest/hang about. That's to slippery stones and back. Its a 700 ft climb.
I'm not certain if you can cross on the dam half way down Derwent, so if you go all the way down to the bottom of Derwent it adds another 10 miles, sorry for the poor guestimates. Should have sorted this out better huh, it will be easy going as on one side its tarmac almost all the way and the other is hard pack hardcore.
Sorry i've only just got all this in stone but well ya know... I'm new to organising, im normally a mere sheep
That is from car park to slippery stone (where I have highlighted with big arrow, then down round derwent and then back to slippery stones. So add another 5 miles on the end and bam, 20 mile ride.