Point of detail - this picture is of Long Pond, which is towards the east of the Common, near where Rookery Road crosses it, and a considerable diversion from the apparent route along the A205.
Mount Pond is close to the A205, just north of Windmill Drive, and Tom's Kiosk is on the southern edge of it. It's open 24/7 and very popular with cabbies and coppers, so not somewhere you could ever count on being unobserved. OTOH, how much notice would someone on a tea break take of people wandering round the parts not right by the kiosk? Police were searching the banks of this pond from the water thus morning.
There are two other ponds on the Common - *advertiser censored* Pond, currently drained, and used as a paddling pool in the summer, and Eagle Pond which is close to the A24 not far from the A205 but definitely to away to the side for someone going down the south circular.