Ian Buist was the quintessential Civil Service mandarin, but also a doughty proponent of social progress. He had a fearless determination to champion the rights of the victims of injustice, minorities and the marginalised.

Probably the proudest achievement of his later life came in 1979 when, as an Under-Secretary in the Foreign and Commonwealth Office, he persuaded, almost single-handedly, the First Division Association to support full equality for lesbian and gay people. This put the FDA ahead of many other professional associations. Using his deep sense of fair play and formidable drafting and lobbying skills, he achieved a notable victory against an indifferent, if not hostile, executive.

Earlier, Buist had been one of the chief architects of the policy to remove from white settlers in the highlands of Kenya their legal, but plainly racist, privileges over land ownership and inheritance. These changes helped to pave the way for independence and a widespread respect among many Kenyans for his role in the transition from colony to statehood. Throughout his life he retained a deep interest in Kenyan affairs. He often noted that most Kenyans had no time for the Mau-Mau, and how closely post-independence Kenyan government policy mirrored the earlier policy of the British.

Injustice was anathema to him, motivated much of his life’s work and cost him the highest promotion. A man with such views, and who listed from 1978 his membership of the Lesbian and Gay Christian Movement in Who’s Who, proved too much for some in authority.

After Winchester, and New College, Oxford where Buist obtained a congratulatory double first in classics, he began his career in 1952. Having come top in the Civil Service examinations he had the choice of any department. He chose the Colonial Office and soon found himself immersed in the highest levels of government policy-making which remained his métier throughout incarnations in the Civil, Colonial and Diplomatic Service.

John Latto Farquharson Ian Buist was born in 1930, the son of a Scottish army doctor and a mother who was the first woman president of the Students Representative Council at St Andrews. His later embrace of Christianity through his allegiance to the Church of Scotland/United Reformed Church, of which he remained a lifelong member, gave him his philosophical lodestar.

This led him to advocate enlightened and progressive policies as an adviser to successive administrations in pre-independence East and Central Africa through the 1950s, and especially when resident in Dar es Salaam from 1962 to 1969. He constantly sought ways of expanding education, strengthening health infrastructure, embedding the judiciary, broadening democracy, improving water supplies, sanitation and drainage, and empowering indigenous politicians, often by devising subtle schemes to undermine the least savoury aspects of colonialism. After his career began it was not long before he was singing, a lifelong passion, in the Colonial Office Choir, in which he sang at the Coronation.

Assigned to the East Africa Department he was sent as secretary to a commission investigating the Kenya Police which led to him later joining Amnesty International. The commission’s job was to overhaul the structure, organisation and conditions of service. The Kenya Police in those days was set up on racial lines: European, Asian and African. Buist was determined to abolish the grading on racial lines without hurting too many feelings.

It was when he moved to the Economic General Department of the Colonial Office in 1961 in the era that gave rise to what became known as Overseas Aid, now International Development, that Buist’s future path was determined. He was among the first to be involved in the formulation of policies which gave rise to co-ordinated global inter-governmental technical and assistance programmes, coinciding with the activities of the World Bank. Buist never looked back and found endless stimulation in administering a sizeable budget designed to lift millions out of poverty, alleviate suffering and promote education.

Like every gay man, especially in pre-1976 Britain, he knew from direct experience how entrenched homophobia could wreck or undermine lives. He was not a little surprised to survive “positive vetting” in 1974. His Permanent Secretary, Sir Geoffrey Wilson, overruled the security services to whom Buist had freely and unselfconsciously declared his sexuality. But the ordeal was one of the most stressful of his life since it pitted his honesty and integrity against the prevailing Civil Service code which viewed homosexuals as possessing a “serious character defect”. He was fortunate in having a Quaker (although he did not know it at the time) as his boss. For someone in the higher echelons of the Civil Service his membership of the Campaign for Homosexual Equality from 1972 was unusual, if not daring. He was in his early fifties when he found his closest life-partner, Dennis Regensburg, whose death eight years later, in 1988, in an accident in Pakistan left Buist desolate.

In retirement Buist devoted more than 20 years’ service to the board of Plan International UK, making his experience available to the charity’s global work in child-focused community development. He wrote numerous outstanding submissions to government consultations on behalf of the Lesbian and Gay Christian Movement.

Despite his progressive and prophetic views, he fully respected Civil Service proprieties and could never be accused of partisanship. This, coupled with his gifts for leadership, energy, friendship and clear logical thinking, accounted for the promotions which came his way.

He was appointed CB in 1990.

Buist died peacefully, surrounded by a number of friends from around the world and devoted family members.

Ian Buist, CB, colonial officer, overseas aid administrator and champion of human and gay rights, was born on May 30, 1930. He died on October 19, 2012, aged 82.

Memorial Service: Trinity United Reformed Church, Wimbledon SW19 4AA, 2pm, 15 March 2013. All Welcome.