[2]: 741 He nurtured the careers of a number of distinguished journalists and writers, including Roland Bird, Donald Tyerman, Barbara Ward, Isaac Deutscher, John Midgley, Norman Macrae, Margaret Cruikshank, Helen Hill Miller, Marjorie Deane, Nancy Balfour, Donald McLachlan, Keith Kyle, Andrew Boyd and George Steiner.

The result was The Crowther Report – Fifteen to Eighteen,[3] which eventually led, in 1972, to the raising of the school-leaving age to 16, and in which he coined the word 'numeracy'.

[5] He was editor of Transatlantic, a magazine published in the 1940s by Penguin Books, and was a regular participant on The Brains Trust on BBC radio.

[2]: 758 In education, he was a member of the governing body of the London School of Economics,[2]: 758  and in 1969 he was appointed Foundation Chancellor of the Open University.

[2]: 867  His appointments included vice-chairman of Commercial Union, chairman of The Economist Group, Trust Houses Group, Trafalgar House and Hazell Sun as well as director of London Merchant Securities, Royal Bank of Canada, British Printing Corporation and Encyclopædia Britannica, Inc.

His younger brother, Bernard Martin, followed him to Clare, from where, after obtaining a PhD in Physics and collaborating with Mark Oliphant, he, like Geoffrey, was awarded a Commonwealth Fund scholarship in 1939.

[6] The youngest of the three brothers, Donald I. Crowther, obtained a first in natural science at Magdalen College, Oxford and became an associate editor at the BMJ.

They had six children, one of whom, Charles, went on to study economics at Corpus Christi College, Cambridge, and became a journalist at the Financial Times,[7][8] while another, Anne, was a prominent member of the Greater London Council prior to its dissolution in 1986.

Their eldest child, Judith Vail, died in a car crash outside Boulogne-sur-Mer on 11 July 1955, aged 20.