Tomorrow marks the 75th anniversary of a momentous occasion during World War II. It is likely to be the last Memorial Day at which the remaining members of the ‘few ’ will be fit enough to take part

May 1, 1939: Spitfires from No.19 Fighter Squadron, based at Duxford, Cambridgeshire.

In the midst of World War II, Prime Minister Winston Churchill uttered the immortal words: “Never in the field of human conflict was so much owed by so many to so few.”

The use of the “few” in Churchill’s speech to Parliament on August 20, 1940, referred to the heroic Allied airmen of the RAF who had repelled the threat of German invasion.

A total of 544 RAF personnel from Fighter Command died defending the UK from the Germans in the summer and autumn of 1940, about one in six of those who fought.

Scores more from Bomber Command and Coastal Command died as the battle for national survival was waged in the skies during the dark days of WWII.

The average age of an RAF pilot in 1940 was about 20 years. Some were as young as 18 and there were others who were over 30.

It was a fact that, with the age of most pilots at around 21, many of the RAF’s Battle of Britain pilots were not old enough to vote but not too young to die for their country.

This year’s 75th anniversary is predicted to be the last at which the remaining members of the “few” will be fit enough to take part, according to the Battle of Britain Memorial Trust.

Today, the air crew are remembered on the Battle of Britain Memorial at Capel-le-Ferne in Kent and on the Battle of Britain Monument in London

Around two-thirds of the 3,000 or so RAF Battle of Britain pilots were officers who could expect to earn £264 a year, roughly the equivalent of just over £30,000 a year today.

But not all the airmen were British, with Fighter Command having quite a cosmopolitan mix, including Poles, Belgians and Czechs.

The Battle of Britain began as Hitler turned his attention across the Channel after defeating the French.

September 30, 1940: Soldiers from the 9th Battalion, The Devonshire Regiment, guarding a Luftwaffe Messerschmitt Bf109E, which crash-landed following a dogfight near Beachy Head, East Sussex.

The Germans began air attacks in the early summer, designed to seize control of the skies over England in preparation for invasion.

RAF pilots had one significant advantage over the Germans – they were defending their homeland.

High above the pastoral landscape of Kent and Sussex, Britain’s future was placed in the hands of this 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 around five to one.

The RAF scrambled its Spitfire and Hurricane pilots 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.

The Luftwaffe lost almost 2,000 aircraft in the battle, while the RAF lost more than 900.

On September 15, 1940, RAF Fighter Command claimed victory over the Luftwaffe after a day of bombing raids ended in heavy losses for Germany.

Shortly after, Hitler postponed and then cancelled invasion plans, turning his attention to the defeat of the Soviet Union.

And so it was that Churchill said to Parliament on August 20, 1940: “The gratitude of every home in our island, in our empire and indeed throughout the world, except in the abodes of the guilty, goes out to the British airmen who, undaunted by odds, unwearied in their constant challenge and mortal danger, are turning the tide of the world war by their prowess and devotion.

“Never in the field of human conflict was so much owed by so many to so few.”