Upon completion of his Ceylon contract he gained a new appointment in Katha, Burma, but it was cut short by a bad attack of typhoid fever with malaria and he was sent back to England on six months' sick leave.

He enlisted in September of that year and was granted a commission in the Royal Field Artillery as a second lieutenant, and was quickly placed in command of B Battery, 72nd Brigade RFA.

In 1924 he purchased a Gordon England special Austin Seven and despite his disability began racing regularly at Brooklands Motor Circuit.

He suffered a crash during the 1932 RAC Tourist Trophy race at Ards in Northern Ireland that further worsened the disability to his already damaged leg.

[1] Public acclaim persuaded the Nuffield Group to provide financial support, enabling the modification of another MG K3, EX135 which was given a streamlined body by Reid Railton.

[1] In 1939, alongside his old friend Sir Malcolm Campbell, Gardner was part of the Coats Mission, a secret plan to evacuate the Royal Family from London in the event of a German invasion.

In 1944, he was promoted to lieutenant colonel and posted to 21 Army Group HQ, acting as a Civil Affairs officer in General Montgomery's headquarters during D-Day, a job he continued until the end of the war.

[1] In September 1948, after a falling out with MG, Gardner linked up with Jaguar Cars who agreed to support him for another run in Jabbeke.

[7] In 1951 and 1952, with renewed support from the MG Car Company, Gardner took EX135 to Bonneville Salt Flats, Utah, setting a total of 43 short- and long-distance speed records.