The foliage skirts of the oaks and chestnuts, hems flapping in the breeze, soon give way to the Serpentine and its green silted waters, Italian fountains and arched bridge. I walk along a railed fence, past Peter Pan being assaulted by tourists, past thick undergrowth and then ripening elderberry and clawing blackberry, its hard green fruit just starting to hint at purple. I half expect Peter Rabbit to come squeezing through the railings but I settle for a hen thrush instead, which scurries across the path in front of me. Under rustling beech leaves old men remove their shoes and socks and wriggle their toes in the turf. Families break open lunches. Kids play hide and seek. A scotch thistle gives up its crown, and seeds lift away on the breeze which, incidentally, carries to me the turbo-fan whine of the unending stream of aircraft on long finals into Heathrow. These gardens are a plane spotters delight.