Battle of Britain veterans will today be joined by members of the Royal Family for a thanksgiving service at Westminster Abbey.
Prince William, fresh from graduating as a Search and Rescue Force helicopter pilot, will attend the mass with his father, the Prince of Wales, and the Duchess of Cornwall.
The ceremony celebrates the 70th anniversary of the pivotal Second World War battle in which Britain's pilots defeated the Nazi threat in the skies of southern England.
The Battle of Britain began as Hitler turned his attention across the Channel after defeating the French.
The Germans launched air attacks in the early summer designed to seize control of the skies over England in preparation for invasion.
High above the pastoral landscape of Kent and Sussex Britain's future was placed in the hands of a small band of young fighter pilots.
Day after day the Germans sent bombers and fighters over England, with RAF pilots outnumbered in the air by four to one.
The RAF scrambled their Spitfire and Hurricane aircraft into the sky to do battle often three, four or five times a day. Britain's air defence bent, but did not break.
Nearly 3,000 air crew served with Fighter Command during the course of the battle, nearly 600 of whom were from the British Dominions, and occupied European or neutral countries.
Shortly after, Hitler postponed and then cancelled invasion plans, turning his attention to the defeat of the Soviet Union.
In appreciation of the RAF pilots' heroic effort, then prime minister Winston Churchill famously said: "Never in the field of human conflict was so much owed by so many to so few."
Earlier this week a statue was unveiled in central London to commemorate one of the battle's unsung heroes.
Air Chief Marshal Sir Keith Park, a New Zealander, commanded the squadrons throughout that fateful summer.
There will be a flypast following today's service.
Modern day RAF fighter pilot Flight Lieutenant Jonathan Davy, 44, said he would have loved to have flown in the Battle of Britain.
Speaking before today's service, the Typhoon fighter pilot who has served in Iraq said the nation owed a huge debt of gratitude to everyone involved in the Battle.
He explained: "What those pilots did defines everything as you think of yourself as a fighter pilot.
"It's a huge, huge legacy to live up to, as a kid growing up in the 1970s and 1980s there were so many Battle of Britain films and RAF air shows it was something I had aspired to ever since I was a small boy.
"The realisation that I had got to fly the successor to the Spitfire was quite magic."
He said that if the whole of the RAF hadn't performed as they did during the battle the nation may not have survived.
He added: "It's impossible to overstate the importance of the Battle of Britain, the whole country did have to fight as a team, that is why there is so much memory of the battle.
"It was defence of the realm against a very well defined and potent threat."
Sir Stephen Dalton, Chief of Air Staff, said winning the Battle of Britain was vital to the overall outcome of the war.
Speaking outside Westminster Abbey he said: "The importance of today is of course to recognise the veterans who are still here and all those who gave their lives to ensure that the Battle of Britain was won and the freedom of this country was assured.
"Unless we had control of the skies over Britain we could not build up the forces ready to liberate Europe later on.
"Of course that is entirely relevant today, without the freedom of the skies in Afghanistan it is well recognised that there would need to be 10 times the number of soldiers and marines on the ground to achieve the same effect.
"It is the aircraft and helicopters that allow our forces and our allies to prosecute the war project against the Taliban as effectively as we can."Reuse content