Well this morning I did the same route as W1R1 which starts fairly gently uphill, goes downhill quite steeply just when the first run starts (have to be careful there!), continues downhill more gently for a while, then is basically flat with one steep uphill bit and a long grind uphill back home. Felt really good on the flat bits, OK on the gentle bits and very annoyed with myself when the very steep uphill hairpin bend loomed just as I was going into the 5th run. The sound of an approaching car was enough to keep me going up and round that corner very slowly but without stopping, which was very satisfying.
The surprising thing was how far I went today. On W1R1 it took 32 minutes to get round albeit with a short detour when I missed a turning (adding say 3 minutes to my route). However, today I started the last run AFTER I'd gone past my house, so I must have got there in just over 22 minutes! Not going for speed, but pleasantly surprised that I must be a bit fitter to have got round quicker. Presumably I'm walking more quickly as well as running a bit better on the flat - and it must help knowing the route and not adding on little detours!