Ramanathan worked for the British
Inland Revenue for a while before returning to Ceylon. He became an
advocate of the Supreme Court and
practised law. He joined the
Attorney-General's Department in the late 1970s as a crown counsel. He was appointed to the High Court in 1978 and served in
Matara,
Anuradhapura,
Kurunegala and Colombo. In 1985 he was appointed to the Court of Appeal. He was later promoted to President of the Court of Appeal. He was then appointed to the Supreme Court. Ramanathan was elected
Master of the Bench by
Gray's Inn. He was also president of the British Scholars' Association, president of the Medical-Legal Society, member of the council of the Indo-Pacific Association of Law and Medicine and a member of the
Permanent Court of Arbitration in The Hague. Ramanathan was awarded the
Deshamanya title, the second highest civilian honour in Sri Lanka, by
President Chandrika Kumaratunga. ==Later life==