Selwyn Macgregor Grier was born in Apr 1878, the only son of the Rev. R.N. Grier, Vicar of Hednesford, Staffordshire, and of his wife Grace. He was educated at Marlborough College and Pembroke College, Cambridge, where he was a classical scholar, graduating BA (later MA) in 1900, and achieving a French and English special in 1901.

From 1901, Grier taught at Berkhamsted School, and from 1902 at Cheam. He joined the Colonial Service and became Assistant Resident in the Zaria Province of Northern Nigeria in 1906. He spent five years in Zaria, taking charge of the Province for periods in 1910 and 1911, and was transferred to Bauchi in 1912, and then to Ibadan the following year. From 1921 to 1925, he was Secretary for Native Affairs, and during this period was requested to tour and made recommendations on provincial administration (MSS. Afr. s. 1379/3, folders 6 and 8). In 1922, he married Florence, daughter of Dr C.G. Heard of Yorkshire.

In 1925, Grier was seconded as Director of Education, Southern Provinces. He resigned from the Secretaryship in order to devote himself to establishing a proper basis for the country's education.

In 1929, he was transferred to Trinidad as Colonial Secretary, and became Governor of the Windward Islands in 1935. The onset of blindness caused his resignation in 1937, but he continued to work for colonial interests. An account of his career is given in an obituary notice (MSS. Afr. s. 1379/2, folder 20, fol. 8). His services were rewarded with the CMG (Companion of the Order of St Michael and St George) in 1929, and in 1934 he became Knight Bachelor and a KCMG (Knight Commander of the Order of St Michael and St George) two years later. He died on 8 Nov 1946.