Documentary charting the build up to the 75th anniversary of Battle of Britain Day on September 15, 2015. An estimated 40 Spitfires and Hurricanes from across the UK, USA and Europe will come together at the Boultbee Flight Academy, the world's only Spitfire Flying School, to take part in an historic flypast over the South of England. Dermot O'Leary hears the memories of veterans who have come to witness it.