Amerasinghe was the close cousin of famed Sri Lankan nation builder Samson Felix Amarasinghe,OBE, (correct spelling Amerasinghe).They were close allies throughout his life.
Amerasinghe joined the Ceylon Civil Service in 1937, starting a career that would span 44 years. As a cadet, he served in the Kegalle Kachcheri, as the Additional Police Magistrate in Kegalle and office assistant, Jaffna Kachcheri. Promoted an officer, he served in the Puttalam, Mannar and Vavuniya Kachcheri, before appointment as Secretary to the Minister of Health in 1941. He then served as Assistant Controller of Imports and Exports, Assistant Government Agent, Kegalle, Rathanapura and Matale. He was then Assistant Secretary to the Ministry of Home Affairs. In 1950, he was appointed Resident Manager of the Gal Oya Development Board in 1950. Two years later, he was sent on his first overseas appointment as Counsellor of Embassy of Ceylon in Washington, DC, from 1953 to 1955. From 1955 to 1957, he was the Controller of Establishments, General Treasury. In 1958, he became the Controller of Finance, Supply and Cadre, General Treasury. The same year, he was appointed as the Permanent Secretary to the Ministry of Nationalized Services and Road Transport as well as Chairman of the Port (Cargo) Corporation.[2]
In 1963, he was appointed Ceylon High Commissioner to India and served concurrently as Ambassador to Nepal and Afghanistan until he moved to the United Nations in 1967.
United Nations
Amerasinghe was appointed Ceylon's Permanent Representative to the UN in 1967, a post that he would hold until 1980. At the UN, he held several key positions, which included Chairmanship of the United Nations Ad Hoc Committee on the Peaceful Uses of the Sea-Bed and the Ocean Floor beyond the Limits of National Jurisdiction, President of the United Nations Conference on the Law of the Sea and chairman United Nations Sea-Bed Committee. Amerasinghe was also the Chairman of the Ad Hoc Committee on the Indian Ocean, which Sri Lanka proposed be designated as "zone of peace". He has chaired the committee when it was created in 1973. Also, since its creation in 1969, he has been Chairman of the Special Committee to Investigate Israeli Practices Affecting the Human Rights of the Population of the Occupied Territories.
While serving as Permanent Representative, he held concurrent accreditation as Sri Lanka's Ambassador to Brazil.
He was re-elected chairman of the Conference on the Law of the Sea in 1980 after he had left Sri Lanka's delegation to the United Nations. The Economist styled him the two-million-dollar chairman, after the cost of the conference.[4]
Death
He died on 4 December 1980 in New York, USA. For his services for the Law of the Sea, a fellowship in his name has been created by the UN.[5]
H.S. Amerasinghe Fellowship, United Nations, division for oceans & law of the sea, 24 August 2012, retrieved 27 March 2014, The Hamilton Shirley Amerasinghe Memorial Fellowship (HSA) was established in 1981, in memory of the late Hamilton Shirley Amerasinghe, the first President of the Third United Nations Conference on the Law of the Sea (1973–1980), in recognition of his contribution to the development of the law of the sea. The late Ambassador Hamilton Shirley Amerasinghe of Sri Lanka had been Chairman of the Ad hoc Committee to Study the Peaceful Uses of the Sea-Bed and Ocean Floor from 1967 to 1970 and subsequently, of the Standing Committee for the Peaceful Uses of the Sea-Bed and Ocean Floor beyond the Limits of National Jurisdiction, from 1970 to 1973 HAMILTON SHIRLEY AMERASINGHE MEMORIAL FELLOWSHIP ON THE LAW OF THE SEA
