In September 1939 Johnston joined the 2nd Battalion Grenadier Guards, and was sent for officer training to Sandhurst after which he was posted to the Grenadiers Training Battalion, based at Windsor, in the spring of 1940 where he served as a Technical Adjutant.
Johnston joined the 2nd Battalion Grenadier Guards. This was in September 1939. Johnston was sent for officer training to Sandhurst after which he was posted to the Grenadiers Training Battalion in the spring of 1940 where he served as a Technical Adjutant. This was based at Windsor. This was in September 1939.