Blimey. Never mind.
Suggestion:
1. Train it to Kingston SW mainline railway station.
2. Run half a mile to the River Thames.
3. Run along the River Thames path from Kingston to Richmond.
4. Just before Richmond, proceed up the hill and into Richmond Park via Richmond Gate.
5. Run halfway round (or across) Richmond Park by whatever route you want, exiting via Robin Hood Gate.
6. Cross the A3. (They've put in traffic lights for pedestrians now, so it's safe and easy to cross.)
7. Proceed around (or across) Wimbledon Common by whatever route you want, ending up at Wimbledon Village.
8. Run down Wimbledon Hill.
9. Train it home.