Francis David Langhorne Astor, known as David, was born 5 March 1912 at his family’s London home in St James Square, the third child of Waldorf, 2nd Viscount Astor and his wife Nancy Witcher Langhorne Astor. He was primarily brought up at Cliveden, surrounded by his parents’ social network, which included individuals such as Welsh educationalist and civil servant Thomas Jones (T.J.), who was to have a lasting influence on him. He was educated firstly at West Downs School and then at Eton. Astor gained a place at Balliol College, Oxford where he studied Politics, Philosophy and Economics, and became acquainted with German Rhodes Scholar Adam von Trott, who would later be known as a member of the 20 July Plot to assassinate Hitler. He struggled at Oxford, suffering from bouts of depression and after two years, decided to take six months out of his studies to work in an engineering firm in Glasgow, with the idea of getting some experience of how “ordinary people” lived. In the end, he did not return to Oxford to finish his degree.

In the years running up to the war Astor worked briefly as a clerk at merchant bank Lazard’s, then as a journalist on The Yorkshire Post, and, at his father’s behest, became increasingly involved with The Observer. In 1940 Astor enlisted in the Royal Marines and was a press officer for Combined Operations in Whitehall. In 1944 he took part in a mission in France and was wounded in the shoulder.

In 1946 Astor formally joined The Observer as its foreign editor, and in 1948 when Waldorf Astor transferred ownership of the paper to his sons, David was appointed the editor, a role he held until he retired in 1975, after which he remained a director. Under his editorship, The Observer acquired an eccentric character, with writers such as George Orwell and Arthur Koestler and campaigning on some of Astor’s particular areas of interest, notably apartheid and anti-colonial movements in Africa. For the most part the paper was a commercial success, although this faded somewhat when the paper campaigned against the invasion of Suez.

David Astor held an active interest in many areas, including organic farming, psychoanalysis, the Middle East, peace studies and prison reform, and most the campaign for the release of Myra Hindley. He was also a major financial supporter of charities including Chiswick Family Aid, which in 1993 would become Refuge, Amnesty International and the Prison Reform Trust.

Astor was married twice, firstly from 1945 until 1951 to Melanie Hauser, with whom he had one daughter, and from 1952 until his death to Bridget Wreford, with whom he had five children.