To the police, the area of Notting Hill circumscribed by the carnival route is like a patch of fields that are first to be irrigated with people and than drained of them, all in the same day. Like some ancient farmers working quietly and patiently in concert, they know exactly what they are doing with more than one-million rowdy but jolly people without any particular aim but to have loads of noisy fun. In the early afternoon, they make sure all the streets within the area are more-or-less evenly filled; in the evening, they make sure they are evenly emptied; at all times they keep the entry and exit points open to ensure an even and free flow in and out. They are real masters when it comes to the flow of people, who come to the carnival in rivers streaming out of the underground stations around Notting Hill. At nightfall, the flow will change direction, and the shrinking rivers will drain into the same caves. Guided by police helicopters that hover above, police squadrons now open one sluice, now close another. The intersection of Artesian Road and Chepstow Road—above which I hover, as it were—appears to be a safety valve: when the top of Chepstow Road chokes up, the flow that comes up from Westbourne Grove is diverted into Artesian Road. Shortly afterwards, the squadron stands aside or moves to another intersection, another safety valve in need of adjustment, and things return to normal at my station.