On 18 February 1920 he and Captain C. F. Gordon shot down an enemy operated Sopwith 1½ Strutter Grigson was Mentioned in Despatches on 31 March 1920. From February 1920 he commanded a flight of Airco DH.9s belonging to No. 55 Squadron RAF in Egypt. The Squadron reformed on 1 February 1920, when No. 142 Squadron, based at Suez was re-numbered. It started to receive Airco DH.9A aircraft in June 1920, and was equipped with a mixture of DH.9s and DH.9As when it transferred to Turkey in July to support British forces occupying Constantinople and the Dardanelles.