[12] According to his brother Ross, during his time there, Johnson was nearly expelled after refusing punishment for a misdemeanour, believing it to be unjustified: "he was very principled and simply dug his heels in".

He applied to join the Auxiliary Air Force (AAF) but encountered some of the social problems that were rife in British society.

The prospect of war increased in the aftermath of the Munich Crisis, and the criteria for applicants changed as the RAF expanded and brought in men from ordinary social backgrounds.

He joined the Territorial Army unit because, though he was in a reserved occupation, if war came, he had "no intention of seeing out the duration building air raid shelters or supervising decontamination squads".

One day while riding through Burghley, near Stamford, on annual camp Johnson took a detour to RAF Wittering nearby (now in Cambridgeshire.)

The wing commander agreed, but nonetheless, Johnson was selected for fighter pilot training and given the service number 754750 with the rank of sergeant.

After training was complete on 7 August 1940, Johnson received his "wings" and was immediately inducted into the General Duties Branch of the RAF as a pilot officer with 55 hours and 5 minutes solo flying.

Johnson had his harness straps on too loose, and wrenched his shoulders – revealing that his earlier rugby injury had not healed properly.

[28] Johnson's old injury continued to trouble him and he found flying high performance aircraft like the Spitfire extremely painful.

RAF medics gave him two options; he could have an operation that would correct the problem, but this meant he would miss the Battle of Britain, or becoming a training instructor flying the light Tiger Moth.

Johnson often found himself flying alongside Wing Commander Douglas Bader and Australian ace Tony Gaze.

Flight Lieutenant Eric Lock and Wing Commander Paddy Finucane were killed on Rhubarb operations in August 1941 and July 1942 respectively.

After a long conversation into the early hours, Bader accepted the suggestions by his senior pilots and agreed to the use of more flexible tactics to lessen the chances of being taken by surprise.

During this battle Adolf Galland, Geschwaderkommodore (wing commander) of JG 26 was wounded; his life was saved by a recently installed armour plate behind his head.

On that day Douglas Bader had been without his usual wingman Sir Alan Smith who was unable to fly due to having a head cold.

The formations fell apart and the air battle became a mass of twisting aircraft; It seemed to me the biggest danger was a collision rather than being shot down, that's how close we all were.

After an uneventful few months, RAF Fighter Command resumed its offensive policy in April 1942 when the weather cleared for large-scale operations.

Johnson criticised the lack of tactical consistency and when his squadron flew top cover, he often changed to the finger-four as soon as they reached the French coast, hoping his wing leader would not notice.

For the remainder of the year, the squadron was moved to RAF Castletown in September 1942 to protect the Royal Navy fleet at Scapa Flow.

[54] During these weeks, Johnson's wing escorted United States Army Air Forces (USAAF) bombers to targets in France.

[63] Johnson's portrait is included in a montage of eighteen pilots painted by Olive Snell at RAF Westhampnett in 1943; it is now in the Goodwood collection on the same site.

[68] Climbing back to his starting point at 8,000 ft, Johnson attempted to join a formation of six aircraft, he thought were Spitfires.

Johnson's Spitfire IX was hit by enemy aircraft fire for the only time, taking cannon shells in the rudder and elevators.

[75] On another sortie, an enemy transport was sighted, but took evasive action and retreated back to German held territory but Johnson's pilots shot it down.

The German fighters, however, waggled their wings to signal non-hostile intent and Johnson's unit escorted them to an RAF airfield.

Johnson did not leave any written record of his experiences but at the end of his tour received the US Air Medal and Legion of Merit.

[78][77] In 1964 he published his book Full Circle, a history of air fighting, co-written with Percy "Laddie" Lucas, a former Member of Parliament and Douglas Bader's brother-in-law.

[79] Johnson spent most of the 1980s and 1990s as a keynote speaker, fundraiser and spending time on his hobbies; travelling, fishing, shooting and walking his dogs.

A memorial service took place on 25 April 2001 at St Clement Danes and the hymns Jerusalem and I Vow to Thee, My Country were played.

Historian Donald Caldwell has attempted to use what limited German material is available to compare losses and air victory claims but acknowledges the lack of sources leave the possibility for error.