A/C James A. 'Prof' Leathart was born on 5th January 1915.

James initially began his flying training whilst still at university as a member of No 610 Squadron of the Auxiliary Air Force. Joining the regular RAF on graduating, he completed his flying training at No 3 FTS and then joined No 54 Squadron at Hornchurch equipped with Gauntlets. The squadron soon re-equipped with Spitfire I's and owing to the rapid expansion of the RAF he soon found himself a flight commander on the squadron.

On 21st May 1940, James shot down a He 111 in Spitfire P9389 / KL-A near Dunkirk during one of the first engagements by Spitfires over northern France.
The next day he flew a trainer to a French aerodrome to pick up the C.O. of 74 Squadron, escorted by F/O A.C. Deere and P/O J.L. Allen. In spite of the interference of German fighters, the mission was successful and Leathart was awarded the D.S.O. on 11th June 1940 for this action.
By the end of May, James had shot down six more enemy aircraft and had taken over acting command of the Squadron.
He scored four more victories during the Battle.

NB: James was nicknamed 'Prof' because of his academic background and the fact that he had a degree in electrical engineering.

James Leathart (whilst Flight Lieutenant) went to the Supermarine Works at Eastleigh on 3rd March 1939, to collect the first Spitfire (K9880) for 54 Squadron.

James Leathart invented the Oxometer, a measuring instrument of non-existance, with which every new pilot posted to the squadron was tricked. Each pilot would be sent around the camp to collect the Oxometer; when reaching the said place, they would be told, "No, we don't have it. Go try over there." And so the joke carried on, until one bright pilot officer with the help of the station workshops actually built an unusual, but impressive gadget and named it the Oxometer.
They would fill one end of the gadget with soot, and when the unfortunate new pilot was tasked to fnd the Oxometer, eventually came across it, he was of course asked to check the instrument by blowing down one end.
Many a black-mouthed pilot was seen running, much to the amusement of other pilots and personnel, to wash off the embarrassing soot mark around his mouth.

James Leathart put the Spitfire's capabilities, as well as his own, to use on 2nd September 1940 when he "played a game" with the Me 109s:
"I was caught at a disadvantage about 4/5,000 feet below two squadrons of Me 109's. I decided that the best thing to do would be to act as a decoy. I harassed them and weaved among them and ended up getting them about 20 miles away from the aerodrome and north of Rochford."

Citation for the award of the Distinguished Service Order

Acting Flight Lieutenant James Anthony LEATHART (39625).

During May, 1940, this officer led his squadron on a large number of offensive patrols over- Northern France. On one occasion an attack was made on a formation of no less than 60 enemy aircraft. In company with his squadron he has shot down fifteen Messerschmitts, and possibly one Heinkel in and one Junkers 88, during the period mentioned. He also flew a trainer aircraft to Calais Marck aerodrome to rescue a squadron commander who had been shot down there but was uninjured. Whilst taking off, after the rescue, an attack was made by twelve Messerschmitt log's but with great coolness and skilful evasive tactics Flight Lieutenant Leathart succeeded in shaking off the enemy and landing again without damage. Subsequently, he took off and flew back to England unescorted. This officer has displayed great courage, determination and splendid leadership.

(London Gazette – 11th June 1940)