Box Hill is overrated. Avoid the day-trippers, and try a more interesting climb up Barhatch Lane instead. It’s quiet and a little remote, but a beast all the same. The varying gradient all the way up that makes it hard to manage your cadence, topping out at 21% near the summit. Once you've done it, you'll want to do it again. Maybe. Either way, it's worth the trip.
The route is direct, opting for an out-and-back that keeps you relatively fresh for the main climb at the southerly point. When you make it to the top, descend into Peaslake and stop at the Peaslake Village Stores for a pie and coffee while the legs recover.
The route heads back to Richmond Park via Whitedown Lane and then then long Effingham descent, to Oxshott and Thames Ditton.