[2] Barrie served during the First World War in an advisory capacity at the Transport Department of the Admiralty, and latterly in the Ministry of Shipping.

He was the Minister of Munitions representative in Paris during the Peace Conference, and was a Member of the Supreme Economic Council.

He also served as Chairman of the Navy, Army, and Air Force Institutes and as a Member of the Advisory Council to the General Post Office.

On 26 June 1940, he was raised to the peerage as Baron Abertay, of Tullybelton in the County of Perth.

Barrie was also a shipowner and merchant, and held a number of business appointments including as a Director of the London and North Eastern Railway, of the Central Argentine Railway, of the Mercantile Bank of India, of Phoenix Assurance Company, and of Cable and Wireless Ltd.