After being approached by the British Broadcasting Corporation, Gardiner agreed to become the first African to deliver the Reith Lectures. Entitled "A World of Peoples", his six broadcasts in 1965 discussed race relations. The following year he published a book under the same name. He also delivered the Gilbert Murray Memorial Lectures in 1969, the J. B. Danquah Memorial Lectures in 1970, and the Aggrey-Fraser-Guggisberg Memorial Lectures in 1972. In 1969 Ghanaian Prime Minister Kofi Abrefa Busia offered him the office of Secretary of the Presidential Commission and Council of State. Gardiner subsequently wrote a letter of resignation to Thant and made preparations to return to Accra. Meanwhile, members of Busia's cabinet led by Foreign Minister Victor Owusu insisted that Gardiner not be given the post, objecting to Busia's ostensible intentions to "groom" him to be the next President of Ghana. Busia relented and sent a letter to Thant expressing his government's wish that Gardiner remain at the UN. When Gardiner was informed of the decision he was deeply embarrassed and kept his post. In 1972 he was dispatched to Uganda where he attempted in vain to convince President Idi Amin to halt the expulsion of Asian minorities from the country. While at UNECA he served as a mentor to fellow Ghanaian and future UN Secretary-General Kofi Annan.