Esoteric London

Chelsea Embankment, London, SW3. Photo © Roger Dean 2011

From Wikipedia entry ‘London Heathrow Airport’:

Aircraft destined for Heathrow usually enter its airspace via one of four main reporting points: Bovingdon over Hertfordshire, Lambourne over Essex, Biggin Hill over Bromley and Ockham over Surrey. Each is defined by a VOR, (short for VHF omnidirectional radio range), radio-navigational beacon. When the airport is busy, aircraft will orbit in the associated holds. These reporting points/holds lie respectively to the north-west, north-east, south-east and south-west of the London conurbation.

Air traffic controllers at Heathrow Approach Control (based in Swanwick, Hampshire) then guide the aircraft to their final approach, merging aircraft from the four holds into a single stream of traffic, sometimes as close as 2.5 nautical miles (4.6 km; 2.9 mi) apart. Considerable use is made of continuous descent approach techniques to minimise the environmental effects of incoming aircraft, particularly at night. Once an aircraft is established on its final approach, control is handed over to Heathrow Tower.