Peter Cadogan was once described as “Britain’s only professional protester”. That made him an oddity in an age when authority was vested with a trust unthinkable today. His brand of direct action, public dissent and civil disobedience paved the way for the permanent campaigning group.

But Cadogan himself never became part of the PR-driven world of the slick modern pressure group. His life was a long quest for injustices to resist, and philosophical principles upon which to base his resistance. He agitated against nuclear weapons, the Biafran war and Stansted airport, moving from hardline communism to a peaceful utopianism based on the ideals of William Blake.

Peter William Cadogan was born in the North East in 1921. His father worked for a Newcastle shipping company, and Cadogan had a conservative middle-class upbringing. He was sent to public school at Tynemouth and in 1941 joined the RAF Air Sea Rescue Service, serving until the end of the war.

In 1943 he read Lenin’s State and Revolution and later recalled that he was “completely taken in” by “a lethal confidence trick of a book”. He joined the Communist Party immediately after demobilisation, becoming “one of the devout”. In 1946 he went to the University of Newcastle, graduating with a degree in history, and afterwards taught in schools in Kettering and Cambridge, all the time active within the party.

The crushing of the Hungarian uprising opened his eyes. He was suspended from the party for supporting the rebels. The next year he wrote, with the historian Christopher Hill and the journalist Malcolm MacEwen, a party minority report attacking “the concentration of power in a small body of full-time political workers”, for which he was denounced by Moscow. He left the communists, and joined the Labour Party. Soon afterwards he was expelled from Labour for joining a banned Trotskyite group.

By 1960 he had became disenchanted with Marxism. This coincided with the founding by Bertrand Russell of the Committee of 100. Russell had become convinced that the threat of imminent nuclear war made desperate measures necessary, and broke with CND’s more traditional approach, forming the committee to orchestrate large-scale civil disobedience. This culminated in a huge demonstration in Trafalgar Square in September 1961 during which more than 1,000 people, Russell included, were arrested.

Cadogan became involved early on in the committee’s organisation, and played a vigorous part in a group described by The Times in 1968 as “the militant vanguard of the protest movement, pioneer of the sit-down, the peace-chant, and other demonstration techniques which have become universal”.

In 1962 Cadogan attempted to stage a demonstration in Red Square against Soviet nuclear weapons. It was quickly broken up. The next year he gained further notoriety by publicising the founding of Spies for Peace, a group that had revealed the existence of “Regional Seats of Government”, bunkers from which Britain would be ruled in the event of nuclear war. Cadogan became the full-time secretary of the Committee of 100 in 1965, and was able to give up teaching. But by this time the movement had peaked. The civilised world had not been plunged into a nuclear winter, the test-ban treaty had been signed and support ebbed away, with the Vietnam war now the fashionable cause. The committee was wound up in 1968.

Its influence, though, would live on. “Non-stop continuous lobbies are going to be the new factor in the British constitution,” Cadogan said at the time.

Cadogan founded one such lobby, the Save Biafra Campaign, in the vacated office of the Committee of 100. It succeeded in bringing to public attention the humanitarian disaster caused by the war in the seccessionist Nigerian state, but failed to shake the Government’s support for a unified Nigeria.

When the Biafrans capitulated in 1970 Cadogan became general secretary of the South Place Ethical Society in Bloomsbury. This free-thinking society, founded in 1793, had abandoned all religious commitments in the 19th century and acquired a reputation as a leading venue for dissent of all kinds. Cadogan presided there for 11 years, with duties including conducting humanist weddings and funerals.

Cadogan saw it as his mission to defend “rational religious sentiment”, or a sense of the sacred, against militant secularists and his former Marxist allies, but he left after losing a vote of no-confidence in 1981. From then until retirement in 1983 he was a tutor in the history of ideas at Birkbeck College.

Cadogan described himself in 1963 as “a non-violent socialist revolutionary in the English Puritan tradition”. In an admiring article in 1980 Bernard Levin called him “a kind of Philosophical Anarchist . . . far too honest and open a man ever to give his entire allegiance to any ideology” (though Levin did add: “he is probably mad”).

Cadogan’s ideas continued to evolve. He later wrote: “In June 1987 I took stock. I was 66 and had been continuously engaged in movements for freedom, justice and peace for 46 years and seemed to have got nowhere. Something was very wrong. I had either to go back to the beginning and start again, or quit. And there was no way I could quit.” He decided that protest was not enough; “we had to have a positive message to offer”.

He sought to develop a “third way” based on a radical spiritual tradition he traced from the Gnostics through the Anabaptists to Blake. (He was co-founder of the Blake Society and its chairman, 1988–94). Taking Blake’s lines “Man is made for joy and woe, And when that you rightly know Then through life you safely go”, Cadogan sought to develop a political framework that interacted with people as human beings, not as simply voters or consumers.

The practical result of this was a series of organisations promoting “Direct Democracy” (He had written a book under this title in 1974.) Cadogan believed that small groups, where things could be discussed face to face, were the natural political unit (“seven seems to be the ideal number”) and he advocated a radical devolution of power to “community councils”, which make the nation-state redundant.

True to these principles, Cadogan spent many years active in local projects around his home in Kilburn. It was an approach very different to the geopolitical campaigning of his youth, but the results were more tangible. His successes, he said, were “modest but very satisfying”.

He married Joyce, daughter of the Labour MP William Stones, in 1949. They divorced in 1968. He is survived by a daughter.

Peter Cadogan, teacher and campaigner, was born on January 26, 1921. He died on November 18, 2007, aged 86