Pioneer in teaching and practice of human rights

Cedric Thornberry, who has died aged 77, was a pioneer in the teaching of international human rights law who continually sought to use his learning to make the world a better place.

From 1978 onwards he worked with Martti Ahtisaari, then special representative of the United Nations secretary general for Namibia. The task was to open international negotiations and establish a UN presence there in order to release the former South West Africa from the administrative control that South Africa had held over it since the time of the first World War. Thornberry also served the UN in Cyprus, the Middle East and New York.

In the late 1980s, as the question of Namibia returned to the forefront of the UN’s agenda, he joined Ahtisaari in New York to help organise the United Nations Transition Assistance Group (Untag), which supervised and controlled elections in Namibia in 1989. Independence came the following year.

By 1992, Thornberry was in the Balkans. As head of the non-military side of the UN’s peace operation, he persuaded Serbian forces to hand over Sarajevo airport for what became the UN’s largest humanitarian airlift. This eventually became a factor in the lifting of the siege of Mostar.

Born in Belfast, Thornberry came from a family with roots in Tyrone and Fermanagh. He was the elder of two sons of Lila (née Watson) and Laylee, the headteacher of Lurgan Model primary school, Co Armagh, and a president of the Ulster Teachers’ Union. Thornberry attended Finaghy primary school, Belfast, and then Methodist College. Cambridge scholarship In 1954 he went to St Catharine’s College, Cambridge, on an exhibition to read law. He followed his BA with an LLB in international law, and was called to the bar in 1959. From 1958 he wrote on and taught international and constitutional law at Cambridge, and in 1960 moved to the London School of Economics.

He was briefly tempted into politics and stood for Labour, but even in Harold Wilson’s comfortable election victory of 1966 the Guildford constituency, where he stood, remained Conservative. His daughter Emily is currently Labour MP for Islington South and shadow attorney general.

Thornberry greatly admired Harold Wilson's lord chancellor, Lord Gardiner, formerly Gerald Gardiner, and worked with him in the late 1960s and early 70s, particularly in relation to Northern Ireland and the conditions of detention of political prisoners. He was one of the founders of the civil rights movement in Northern Ireland.

His association with Seán MacBride and Amnesty International took him to Greece after the military junta seized power in 1967.

By the time Thornberry left the UN in 1995, he was an assistant secretary general. Thereafter he pursued his activities as lecturer and consultant on peacekeeping and human rights matters, notably as a visiting professor at the Centre for Defence Studies at King’s College London.

He was married and divorced four times. He is survived by five children: Emily, James, Benjamin, Caitriana and Eilise Marie; another son, Peter, died in 2011.