During his time as Secretary General of the All Africa Conference of Churches, Carr moderated the discussions leading to the signing of the Addis Ababa Agreement (1972), which ended the First Sudanese Civil War (1955–1972) in Sudan. He is widely credited with keeping the negotiations on track, and the trust and respect that he engendered was crucial to the success of the talks that produced the Agreement. He was awarded the Knight Great Band in the Humane Order of African Redemption by the Liberian President William V.S. Tubman Jr. and the Grand Corodon in the Order of the Two Niles by Sudanese President Gaafar Nimeiry for his role in mediating the Addis Ababa Agreement (1972).