On July 6th, 1944 Avro Lancasters of 617 Squadron, Royal Air Force (the "Dambusters"), led by Wing Commander Leonard Cheshire, destroyed the Nazi V3 Super Gun site at Mimoyecques in the Pas de Calais region of northern France. This location is very near to the present day entrance to the French side of the Channel Tunnel.
The V3 site was built into a hillside protected by 18 feet (5.5m) thick concrete. To successfully penetrate such a deep structure Barnes Wallis designed 'Tall Boy' bombs were used. Weighing in at 12,000 lbs (5,443kg) the Tall Boy was the world's first bunker busting bomb. They had a very aerodynamic shape with a thicker casing toward the nose. Combined with angled fins this allowed the Tall Boy to fall nose first at a very high terminal velocity whilst also spinning. On impact they would bury themselves deep in the earth and create an earthquake like shock wave that would literally shake the target to destruction.
617 Squadron operated specially adapted B1 Lancasters equipped with SABS (Stabilized Automatic Bomb Sight) to accurately deliver Tall Boy on the V3 target.