I’ve only ridden out that way a couple of times myself. I got a couple of free entries to the London Etape that Human Race used to run out of the Olympic Park. That was slightly longer, going all the way up to the Stanstead airport perimeter fence, and it wasn’t on closed roads so probably used more small lanes than this one.
I think the “big” climb is probably the drag up through Epping Forest near the start and it’s just gently rolling after that. The ramp out of the Limehouse Tunnel is probably the steepest gradient on the ride 