In 1960 civil war erupted in the newly independent Republic of the Congo and Gardiner became heavily involved in UN efforts to resolve the situation, serving as a mediator between various factions and as a close adviser to UN Secretary-General U Thant on the matter.

[3] Gardiner studied at St. Syprian Anglican School in Kumasi[4] before attending Adisadel College in Cape Coast, where in 1934 he was Head Prefect.

[16] Later that year he was hired by Ralph Bunche to work as an area specialist for the United Nations Trusteeship Council[3] with a focus on West Africa in the Section of Territorial Research and Analysis.

[1] In October 1949 he was made the first Director of Extramural Studies at University College in Ibadan, Nigeria, making him the only African department head at the institution.

[21] In his capacity as Establishment Secretary, he drafted a protocol that allowed Ghana to manage its own assets housed in British West African organisations until the relevant neighboring colonies could achieve independence.

Nevertheless, Nkrumah withdrew Ghana's capital from the groups with the stated purpose of ensuring complete monetary independence from the United Kingdom.

Nkrumah considered dispatching him as high commissioner to Pretoria, South Africa, but the idea was ultimately discarded, in part due to the difficulties in finding Gardiner's children the means to earn an education in the region.

[25] By taking the job his political position in Ghana was made neutral, but his overall reputation in the African continent was diminished, as others saw his UN role as an external imposition.

Gardiner moved to UNECA's headquarters in Addis Ababa on 17 May,[26] but following the outbreak of civil war in the newly independent Republic of the Congo he was appointed consultant in public administration to the chief of the civilian mission of the UN Operation in the Congo (known under its French acronym as ONUC) in August 1960 and tasked with helping rebuild the Congolese civil service.

In March 1961 he returned to the Congo at the behest of UN Secretary-General Dag Hammarskjöld to lead a Secretariat mission in negotiating a deal concerning the reorganisation of the Congolese Army.

[27] On 26 July Gardiner was appointed Director of the Public Administration Division at the UN Department of Economic and Social Affairs, making him the highest ranking African in the UN's staff.

[27] He played a key role in mediating the negotiations that resulted in the reconvening of the Congolese Parliament and a ceasefire between UN peacekeepers and the armed forces of the secessionist State of Katanga.

[27] He flew into the Congo on 10 February to assume control of the mission[31] and subsequently garnered significant worldwide media attention in the role.

[35] Upon his return to Addis Ababa, he worked to guard the organisation from controversies and operate it in a non-partisan manner,[36] circumventing African national and continental political disputes and avoiding the causing of offense to governments.

[37] Mindful of the criticism of his predecessor, Mekki Abbas, for being too passive, Gardiner promised that under his management UNECA would take an active role in economic planning and development projects.

Following the foundation of the Organisation of African Unity (OAU) in 1963, Gardiner appealed to the community for cooperation with UNECA in furthering economic growth.

He presented the Articles of Association to the conference for signature and advised that the smaller West African states should attempt to integrate sections of their markets to open themselves up to a wider array of economic activities.

[45] Partly due to his efforts to promote regional economic organisations, Ghana mollified its resistance towards West African integration in the 1970s.

[6] In 1969 Ghanaian Prime Minister Kofi Abrefa Busia offered him the office of Secretary of the Presidential Commission and Council of State.

[48] In October 1972 he was dispatched to Uganda by the UN Secretary-General where he attempted in vain to convince President Idi Amin to halt the expulsion of Asian minorities from the country.

He was also a visiting professor of economics and senior consultant to the newly established Centre for Development Studies at the University of Cape Coast from 1974 until 1977[53] and the chairman of the Board of Directors of the Post and Telecommunications Corporation.

[57][20][58] Two years later the government dispatched him to Nairobi in an attempt to improve relations between Kenya, Tanzania, and Uganda and salvage the financially troubled East African Railways and Harbours Corporation.

[20] According to Africa Confidential, there were rumours that Gardiner had resigned in an attempt to distance himself from Ignatius Kutu Acheampong's economically unstable regime.

[10] "A warm, emotional and intensely human father-figure, whose tolerance and idealism are expressed with a gentle persuasiveness which seems almost out of place in today's bustling and violent world.

[41] He thought increased productivity and higher wages would boost Ghana's economy, and believed that the persistence of a trade deficit would contribute to inflation and national financial difficulties.

[61] He expressed that improved transport and communication systems and rural education and health services as well as land redistribution, participation in global trade, and expanded job opportunity would contribute to development in Africa.

[62] He advocated for the normalisation of relations between African states and the white minority government of South Africa, believing the former could benefit from the economic strength of the latter.

[37] His successor at the UNECA Secretariat, Adebayo Adedeji, felt he lacked a creative outlook, saying of him, "Robert Gardiner was a conservative economist who didn't see anything wrong with the extant development paradigm.

[64] At the opening session of the International Conference for the Study of the Problem of Developing Countries in 1975 he was awarded a gold medal by Italian President Giovanni Leone in recognition for his contributions to Africa.