His father was a partner in the family business of George Frew & Son, sailmakers and cover makers of Paterson Street, Glasgow.
[3] Frew enlisted as a private in the Highland Light Infantry in 1914, and after serving on the front lines in France, transferred to the Royal Flying Corps in August 1916.
45 Squadron was then re-equipped with the Sopwith Camel, and Frew gained his 6th victory on 3 September, two more followed the next day, then another ten by 27 October.
45 Squadron was then transferred to the Italian Front, and Frew gained another seven victories between 11 January and 4 February, bringing his confirmed total to 23.
He received mentions in dispatches on 18 April and 30 May,[10] and on 12 September was granted permission to wear the Silver Medal for Military Valour awarded to him by the King of Italy.
[13] On 5 May 1919 Frew was transferred to the unemployed list,[14] and his award of the Air Force Cross was gazetted shortly after on 30 May.
[10] On 16 December 1925 Frew returned to the Home Establishment, to serve on the staff of the Armament and Gunnery School at RAF Eastchurch,[19] where on 1 July 1927 he was promoted to squadron leader.
[29] On 16 September 1943 his rank of acting air commodore was made war substantive,[30] and from 24 September was permitted to wear insignia of a Commander in the Royal Order of George I with Swords, conferred "in recognition of valuable services rendered in connection with the war" by the King of the Hellenes.
[31] On 15 June 1945 Frew was granted permission to wear the Military Cross, 1st class, conferred by the Belgian government.