The broadcaster and writer Darcus Howe, who has died aged 74, once described himself as having come from Trinidad on a “civilising mission”, to teach Britons to live in a harmonious and diverse society. His aims were radical, and he brought them into the mainstream by articulating fundamental principles in a strikingly outspoken way.

After his initial experience of racial tension in Britain at the start of the 1960s, Howe became active in the Black Power movement in the US and the Caribbean. In August 1970, having returned to London, he organised, with Althea Jones-Lecointe and the British Black Panthers, a campaign in defence of the Mangrove restaurant. Established and run by Frank Crichlow, the Mangrove was a small piece of decolonised territory in Notting Hill, west London. When police attempted to close it, Howe came to his friend’s aid, organising a march. Entirely peaceful until the police intervened in overwhelming numbers, it led to a spontaneous melee, the melee to arrests, and the arrests to the biggest Black Power trial in British history.

For 55 days Howe and Jones-Lecointe led the defence of the Mangrove nine – themselves, Crichlow and six others – from the dock of the Old Bailey. Howe demanded an all-black jury, a claim he rooted in the Magna Carta. The judge rejected this, but the nine had stamped their authority on the case.

Howe subjected the prosecution to forensic scrutiny. Against the combined forces of Special Branch, the Metropolitan police, the judiciary and the Home Office, the nine prevailed, not only winning their acquittal on charges including incitement to riot, but forcing the first judicial acknowledgment that there was “evidence of racial hatred on both sides”. The verdict sent shockwaves through the political establishment. Senior figures in the Home Office manoeuvred behind the scenes to get the judge to retract his statement, but the verdict stuck.

In 1973 Howe established the Race Today Collective. Unlike a traditional political party, members were not trying to set the agenda or to win converts. Rather, they put out a magazine, Race Today, recording grassroots campaigns in Britain and abroad. Among their number were Leila Hassan, the deputy editor and later Howe’s wife, Linton Kwesi Johnson, the celebrated dub poet, Barbara Beese, one of the Mangrove nine, and Farrukh Dhondy, the writer and, from 1984, a commissioning editor for Channel 4 television.

When female Asian workers went on strike at the Grunwick film processing laboratories in Willesden, north-west London, in 1976, the collective provided support. When, the same year, the Bengali Housing Action Group provided an organisational basis for squatting in vacant properties in Tower Hamlets, the collective helped create the largest squat in Europe. This, in time, resulted in an entire community securing decent housing.

Race Today’s largest campaign followed the New Cross fire in 1981. The deaths of 13 black young people from a suspected racist attack in south-east London was met with indifference from Margaret Thatcher’s government, the mainstream press and the police. Howe set about organising a day of action, the largest ever political demonstration by black people in Britain, on a working Monday. In doing so, he applied the methods of organisation that he had learned from the US radicals H Rap Brown and Gwen Patton a quarter of a century earlier.

More than 20,000 people, the vast majority black, marched through London. It proved a powerful demonstration of resolve. Despite oppressive policing, scuffles were rare. But the backlash was swift. Swamp 81, a massive escalation of stop and search, attempted to reassert police control over London’s black community. Tensions eventually reached breaking point, leading to the three days of the Brixton riots – described by Howe as “an insurrection of the masses of the people”. The Race Today office, in Railton Road, Brixton, was on the front line, and the collective monitored the battle, recorded events and, after the insurrection was over, debriefed the leading participants. From then on, Howe argued, no longer would black people simply complain about white power – they would confront it head on.

Howe’s first TV series, The Bandung File (1985-91), was commissioned for Channel 4 by Dhondy, with Tariq Ali as co-editor. Howe reported on topics including pirate radio in London, the economic policies of Julius Nyerere in Tanzania and the overthrow of “Baby Doc” Duvalier in Haiti. In The Devil’s Advocate (1992-96), Howe subjected people in authority to public scrutiny. The series proved popular: as Howe’s producer colleague Narinder Minhas put it, he “brought the intelligent discussions about race to primetime”.

Born in Moruga, Trinidad, Rhett, nicknamed Darcus, was the son of Lucille (nee Rudder) and Cipriani Howe. He was immersed in Dickens, Shakespeare and the Book of Common Prayer by a mother and father who were, respectively, his first teacher and headteacher at Eckel Village primary school. Cipriani was also an Anglican priest, for whom the message of the scriptures was egalitarianism, the gospel of Christ the social revolutionary. Darcus won a scholarship to Queen’s Royal College, Port of Spain, one of the most elite schools in the Caribbean. He divided his time between learning Latin at QRC, attending mass rallies for Trinidadian independence and hanging out with The Renegades, the street gang of urban youth who coalesced around the steel band of the same name in East Dry River.

At the age of 18 he went to Britain with the intention of training as a barrister. However, unwilling to accept the status of second-class citizen, he gave up the law in favour of Black Power politics and radical journalism, and returned to Trinidad.

Meeting Malcolm X in 1965 and Stokely Carmichael two years later made a deep impression on him. In May 1968 he went to participate in the events in Paris. But he soon saw the shortcomings of the self-appointed “vanguard parties” among the Parisian students, and bore in mind the emphasis placed by his uncle, the Marxist historian CLR James, on the importance of the black working class as an agent of change.

Howe found a more effective model of political organisation in the Black Power movement, which was growing in the US and the Caribbean. In October 1968 he travelled to Montreal to participate in the Congress of Black Writers – a Black Power international in all but name. There he discussed the philosophy of organisation with Walter Rodney, and then joined Brown and Patton in organising the Ocean Hill-Brownsville campaign in Brooklyn, aiming to promote black community control of education across New York.

Howe’s next major campaign took place in Trinidad. Working as a journalist for the Vanguard, the newspaper of the Oilfield Workers’ Trade Union, he galvanised support for the Black Power upheavals of February-April 1970. For a time, the revolt brought the government to its knees, and provided Howe with a glimpse of a new society. The squares of Port of Spain were full of black working people debating, reasoning together, organising themselves without the state or capitalism. Patriarchy was also in retreat. Howe took this as a proof of the revolution’s success: for him, Black Power entailed women’s liberation.

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The path that Howe embarked on later that year in London continued into the new century. In his documentaries White Tribe (2000) and the three-part Slave Nation (2001), Howe played the anthropologist, examining Britishness and whiteness. With considerable foresight, these documentaries examined the rise of English nationalism and resentment against Polish migrants. In the 1990s he had a column in the Evening Standard, and for more than a decade he wrote for the New Statesman.

Diagnosed with prostate cancer in April 2007, Howe saw the political significance of the disease. Black men from the Caribbean, America and the west coast of Africa are three times more likely to suffer from it than white men. He worked with the NHS and Channel 4 to encourage black men to have checkups.

Weeks before the riots in English cities in August 2011 prompted by the fatal police shooting of Mark Duggan in Tottenham, north London, Howe wrote a piece for the Voice predicting unrest. He refused to condemn those who took part in it.

One of his last public engagements was the readthrough of Guerrilla, a political drama by John Ridley, to be shown on Sky Atlantic. Howe had spent time with the production team, advising them on the politics of the 1970s and the Black Power movement. They acknowledged the inspiration provided by his involvement in its British arm.

Howe directed his enormous intellectual energy and skill as a political organiser to “bring reason to race”. He rejected the politics of soundbites and prejudice, in favour of a politics based on faith in the creativity of migrant and working-class communities.

He is survived by Leila, three sons and four daughters.

• Darcus (Rhett Radford Leighton) Howe, activist, writer and broadcaster, born 26 February 1943; died 1 April 2017