On leaving the college, Hargreaves worked as a vet's assistant, but he was soon earning a living as a journalist. He also became a copywriter, and script writer for radio and films, and by the late 1930s he had established a reputation for his pioneering approaches to radio broadcasting. His reputation as a communicator went ahead of him and he was recruited to the staff of
General Montgomery to play a role setting up broadcasting services to Allied forces before and after
D-Day. He left the army in 1945 with the substantive rank of major, having briefly held the acting rank of lieutenant-colonel. After the war, Hargreaves continued his media career and during the 1950s was editor of
Lilliput magazine and
Picture Post where he commissioned work from
Bert Hardy. His brilliance as a communications manager led to his being recruited to the
National Farmers Union by
Jim Turner, later Lord Netherthorpe, who was celebrated for his success as a lobbyist for farmers. Working closely with Turner, Hargreaves organised and developed the NFU's Information Department, founding the
British Farmer magazine during an almost intractable crisis of trust between NFU HQ and the members of the largest union in the country, many of whom were experiencing seismic change in the agricultural economy. Hargreaves was deputy programme controller of
Southern Television from 1964 to 1976, in which role he devised new programmes. A lover of
angling, Hargreaves was bemused at the way it had become tribalised by class and species, which he blamed on "sociological, technical, financial and Malthusian" causes. He wrote
Fishing for a Year (1951), in which he argued for "regression" – the pursuit of different fish, in separate places and by varied methods, throughout the seasons. "What do they know of fishing" he wrote "who know only one fish and one way to fish for him?" Yet his language was seldom so polemic and never adversarial. Hargreaves' style was complemented in this first book by the drawings of his friend Bernard Venables: "It is one of the most excellent provisions of Nature" he wrote in a chapter for the warmest time of the year "that
chub are to be angled for on hot summer afternoons ... When the grass is high and full of hum and rustle, when the
comfrey blooms along the edge of the water and the air shivers in the heat, the chub lie just under the surface in slacks and corners and eddies all along the bank. You will see them and you will think they have not seen you". His writing and contacts among anglers saw the president of the
Piscatorial Society, Sir
Robert Saundby, asking Hargreaves to organise the Society's library. With typical thoroughness the collection was removed to Jack's home, later leaving it fully catalogued with not a volume unread. This was when he became sceptical about the opinion of the 17th-century author of
The Compleat Angler,
Izaak Walton, as to the culinary qualities of the chub – a dish Hargreaves described as "eating cotton wool full of pins and needles". ==The Nugent Report==