In 1918 he became Chairman and Managing Director of Explosives Trade Ltd (from 1920 known as Nobel Industries Ltd), a position he held until the formation of ICI.

The merger, orchestrated by Alfred Mond, 1st Baron Melchett and McGowan, created one of the world's largest industrial corporations at the time.

[4] He served as president of League for the Prohibition of Cruel Sports and vice-president of the London Robert Louis Stevenson Club.

[4] He died in July 1961, aged 87, and was succeeded in the barony by his elder son Harry.

Although personally far from wealthy by contemporary standards, McGowan's organisation of the purchase of General Motors shares to the value of £5 million by Explosives Trades Ltd., enabled Pierre S. du Pont's financial rescue of the American car manufacturer from bankruptcy; this episode was naively satirised by Neil Munro in his Erchie MacPherson story "Our Mystery Millionaire", first published in the Glasgow Evening News of 17th May 1920.