http://www.bbc.com/news/uk-england-london-33966632 Never in the field of human conflict was so much owed by so many to so few - Winston Churchill Battle of Britain: Flypast for 75th anniversary of 'Hardest Day' BBC Radio 5 live presenter Lesley Ashmall took this picture and tweeted it with the caption "what a sight!" Aircraft including 18 Spitfires and six Hurricanes are flying over south-east England to mark 75 years since the Battle of Britain's "Hardest Day". The event will recall 18 August 1940, when Bromley's Biggin Hill and other South East military bases came under attack from the German Luftwaffe. It became known as the "hardest day" as both sides recorded their greatest loss of aircraft during the battle. The Battle of Britain lasted throughout the summer of 1940. More than a dozen aircraft line up ahead of the commemorative flypast Pilots make their way to their aircraft at Biggin Hill Airport Crowds of more than 3,000 people have flocked to the airport to see the aircraft It was the first major campaign fought entirely in the air. BBC reporter Clark Ainsworth at Biggin Hill What a sight. Watching those iconic World War Two aircraft take to the skies above Biggin Hill was something to behold. Spectators gasped as they then circled the airfield in formation. The roar of the Merlin engines and the grace with which the Hurricane and especially the Spitfires, climb, bank, dive and weave through the air is a joy to behold. The first few Hurricanes and Spitfires have started to land. In a few minutes time, spectators will be able to walk along the aircraft - see them up close and take pictures. And although they are beautiful to look at on the ground, it is in the sky where they truly shine. Marking the 75th anniversary of the 'Hardest Day' Live updates The Luftwaffe flew 850 sorties, involving 2,200 aircrew, while the RAF resisted with 927 sorties, involving 600 aircrew. The RAF and German Air Force lost 136 aircraft in one day. The special commemoration, staged from the former RAF airfield at Biggin Hill, now a commercial airport, honours the pilots, engineers, armourers, operations staff and ground crews who faced attack that day. Battle of Britain July to October 1940 1,023 aircraft lost by RAF 1,887 aircraft lost by Luftwaffe 3,000 aircrew served with RAF Fighter Command 20% were from the British Dominions and occupied European or neutral countries 544 RAF Fighter Command pilots were killed 2,500 Luftwaffe aircrew were killed Source: RAF.