[1][2] After school he joined Christ's College, Cambridge, graduating with honours degree in mathematics.

[1][3] Mahadeva was called to the bar at Lincoln's Inn and on returning to Ceylon qualified as a barrister-at-law.

[2] He later served as principal of Parameshwara College, Jaffna, a boys school founded by his paternal uncle P.

[1][4] He did not contest the 1931 state council election due to the boycott organised by the Jaffna Youth Congress.

[1][4][6][7] Mahadeva was one of the founding members of the United National Party (UNP) and served as one of its vice-presidents and secretary.

[4][8][9][10][11] 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.

[12] 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.