Sir Ludovic Kennedy was a writer and broadcaster who, with his lifelong friend and colleague Sir Robin Day, set new standards in television journalism. He was a rigorous and charismatic interviewer and reporter, later employing these talents to expose legal injustices and articulate his powerful and provocative views on religion, morality and euthanasia.

With his trademark look of wry bemusement, Kennedy laced his incisive questioning with an idiosyncratic charm that became the blueprint for a generation of journalists and a huge hit with viewers. His poise as a performer was matched by his ability to see through to the truth of a story and take a full grasp of all the issues at play, and it quickly took him to the top of his profession. After rising to early success as a newscaster for the fledgeling Independent Television News, where he worked alongside Day, he blazed a trail with investigative reporting programmes such as Panorama and Tonight.

A strong moral rectitude brought Kennedy into contact not only with current affairs but also with the past. He launched campaigns to reconsider convictions in several high-profile cases, including the hanging of Derek Bentley and the jailing of the Birmingham Six and the Guildford Four. His exposés of corruption and incompetence in the police and legal systems were damningly effective, and he was ubiquitous in debates on the need for judicial reform.

He was an ardent and often outspoken campaigner, also prominent in calls for the legalisation of euthanasia, castigating the Roman Catholic Church’s pro-life stance as “medieval in its thinking and barbaric in its lack of compassion”. Kennedy was already a committed atheist who saw religion as undeserving of any moral high-ground, and he first become involved in the Voluntary Euthanasia Society when his mother, Rosalind, suffering from painful rheumatoid arthritis, told him that she did not want to live any longer. He went on to become president of the Voluntary Euthanasia Society.

A perennially active thinker, Kennedy published a critique of religious doctrine and history of atheistic thought, All in the Mind: A Farewell to God (1999), aged 79. Without any sense of world-weariness, he attacked what he saw as the hijacking of altruism by Christianity, and made a cogent, lively case for the abstract nature of human moral value.

The book also allowed him to chart a much more personal journey. He wrote movingly of his father, a Christian, who died when the ship that he was captaining was sunk off Iceland in the Second World War. Describing the shattering effect of this loss, Kennedy concluded that it aptly illustrated “the uselessness of prayer”. “[My father] had a very simple faith,” he wrote. “He prayed every night and morning of his life, and I know he would have done that on the morning of the battle, and look what happened to him.”

Yet he did not dismiss the potential for spiritual satisfaction in life and was angered at the suggestion that a life without religion might be less moral. He recalled two experiences particular resonant of such spirituality in his life: as a child hearing a piper on the moors in his native Scotland; and seeing hundreds of stars, like “a watchful presence”, while standing on board a fleet destroyer at night during the war.

Kennedy thought of himself as a humanist — a believer in the power of human values outside any religious framework — although he rejected the term itself for having “all the impact of soggy cement”. He was more fond of — and found much solace in — a remark by Leslie Stephen on reading Darwin’s theories of evolution: “I now believe in nothing, but I do not the less believe in morality. I mean to live and die like a gentleman, if possible.”

Ludovic Henry Coverley Kennedy was born in Edinburgh in 1919, the son of Captain E. C. Kennedy and Rosalind, daughter of Sir Ludovic Grant, the 11th Baronet of Dalvey.

The family was prosperous, and Kennedy was sent to Eton, where he was a member of Pop. He then went up to Christ Church, Oxford, where he read English. He played a full part in university life, becoming literary editor of Isis and a member of the Bullingdon, the qualifications for which, he later recalled, were to be “rich, well born and addicted to blood sports”.

When war broke out Kennedy volunteered for the Navy. His father, by then in command of the armed merchant cruiser Rawalpindi, asked his son’s captain if he could take Kennedy on his next patrol. The captain refused, saying that Kennedy was too inexperienced. It was on that patrol that the Rawalpindi was sunk by the German battle cruisers Scharnhorst and Gneisenau.

But Kennedy would get his chance, and always said that the most memorable and exciting period of his life was in May 1941, when he was a 21-year-old sub-lieutenant in one of the Navy’s destroyers, Tartar, which helped to pursue and sink Germany’s biggest battleship, the Bismarck. After the battleship was wounded and subjected to a series of unsuccessful torpedo attacks, Kennedy and his crew went to action stations, and it was not long before the Bismarck was hit. When it burnt and sank, only 110 out of a crew of 2,000 survived.