London has had an air ambulance since 1989, and it began working out of Biggin Hill, but moved to The Royal London on Whitechapel Road in 1990, when it was felt a more central base was needed. Your author still hears it there almost daily as he pedals down the Whitechapel Road, and often sees it in other areas of London, touching down anywhere it can find space, such as on Euston Road in the picture above.
The Ambulance costs £2.25 million a year to run, and is only part-funded by the NHS. The rest of the funding comes from donations to its registered charity, which come from ordinary people and corporate donors, the most conspicuous of which is Virgin, whose logo appears on the side of the helicopter.
For more information, or to make a donation, see http://www.londonsairambulance.com, or find the Ambulance on Twitter at http://twitter.com/TheHelipad