Mahadeva was
called to the bar at
Lincoln's Inn and on returning to Ceylon qualified as a
barrister-at-law. He joined the
Attorney General's Department as a
crown counsel. He was re-elected at the
1936 state council election and in 1942 he became
Minister of Home Affairs. Mahadeva was one of the founding members of the
United National Party (UNP) and served as one of its vice-presidents and secretary. He stood as the UNP candidate for
Jaffna at the
1947 parliamentary election but was defeated by the
All Ceylon Tamil Congress leader
G. G. Ponnambalam. Mahadeva was
Ceylonese High Commissioner to India from 1948 to 1949. Mahadeva was knighted in the
1949 New Year Honours. He was made a
Knight Commander of the Order of St Michael and St George in the
1955 New Year Honours. He was a member of the Public Service Commission from 1950 to 1957. Mahadeva devoted his retirement to cultural and religious affairs. He was a senior trustee of the Sri Ponnambala Vaneswara Temple at Sea Street in Kochchikade, built by his paternal grandfather
A. Ponnambalam and rebuilt by his uncle P. Ramanathan. He was chief trustee of the Sri Arunachaleswarar Temple at
Mutwal, built by his parents. He was patron of the Colombo Vivekananda Society, the Jaffna Saiva Paripalana Sabai and the Colombo North Hindu Paripalana Sabai. Mahadeva died on 8 June 1969. ==Electoral history==