I reckon he won't be riding in Richmond Park very much - unless he wants to lose a lot of time and money getting pulled over by the parks police for breaking the 20mph speed limit. He'll want to be averaging almost 20mph so there are bound to be some downhills where he will go a lot faster.
He manages quite enough laps there already without getting pulled.
I have done several hundred laps of the park and never been pulled (even I can manage laps at over 20mph average). Anyone that rides there regularly knows where the police are and, in general, they are more concerned with cars than bikes. As long as you don't come down a hill towards them, on the wrong side of the road, overtaking cars at 40+mph, they will, in general leave you alone.
It's not the ideal place for big miles most of the time, too much traffic in the daytime, 5 roundabouts to negotiate (which is part of the reason why ACW is quicker), and not flat. But in the early mornings before the gates open and in the evenings once they are locked, then it's a pretty good place if he's happy churning out laps (which he seems to be). It's near his house I think (not actually sure where he lives, but somewhere local, I feel Barnes maybe).
He does several other loops around here, mainly along the roads following the river, so pan flat.
We'll see what he does. I will certainly give him a cheer if he passes me in the park.