Potatoes are bad news for carbs no?
Good ride that, your a better climber than me. In the next couple of weeks Im planning a trip via Raynes Park to Horsley train station then going to do the badass section of the route (Horsley>Newlands Corner>Leith Hill>Dorking>Box Hill), plus cycle home along a good portion of the ride (Box Hill>Leatherhead>Cobham>Esher>Kingston>Wimbledon - about 60 miles total) just to see how far off I am.
I'm expecting the answer to be "quite a lot".
Just hope we can get some guaranteed forecast sun on one of my days off, so I can take my time with it.
EDIT: Just plotted it out to a TCX file for my Garmin. Looks a great challenge for me, but going to have to bite the bullet sooner rather than later. 53.4 mile route, elevation +3,328 ft / - 3471 ft, almost all that the first 26 miles...