Plan is to ride to Haggerston from Canada Water, arriving there at 12.30.  Then take the Overground back to Canada Water, getting there by 1pm (so bring Oyster card or other method of paying; it is a Zone 1-2 fare).  Proposed route is: Along river to Greenwich, through the foot tunnel, round east side of isle of Dogs, continue north to Lee Navigation, follow this to Olympic Park, then across to Victoria Park and along the Regents Canal to Haggerston.  Should be able to reach the Velodrome and have a short break.  Flat ride,13 miles, with lots of off-road.  Route at https://goo.gl/VkVHt4