After a short probationary period at Oxford, he was posted to the North-Western Provinces and Oudh in 1885 (which later became the United Provinces of Agra and Oudh), where he was director of land records between 1897 and 1899 and financial secretary to the government between 1899 and 1903.
From 1905 to 1906 he briefly left India to act as an adviser to the Cape Colony and Transvaal governments in South Africa.
He remained in this position until 1918, when he became finance member of the Viceroy of India's executive council.
After the war, Meston, along with Lionel Curtis, was the main designer of the Institute of International Affairs, and served as chairman of its first governing body from 1920 to 1926, of its publications committee and of the editorial board of International Affairs.
Lord Meston died in October 1943, aged 78, and was succeeded in the barony by his only surviving son Dougall.