Elected to the first post-independence parliament, he was one of the founding members of the Sri Lanka Freedom Party.

Born Nissanka Herbert Mendis on 17 January 1898 at his maternal grandparent's home, Garumuni Walawwa in Balapitiya, to Anoma Wickramaratne De Zoysa and Nissanka Diveris Mendis, a clerk in the Ceylon Government Railway.

[1][2] Sri Nissanka entered politics having been elected to the Colombo Municipal Council in January 1944.

He contested the 1952 general election from Kurunegala as an independent candidate, but was defeated by Dingiri Bandara Welagedara from the United National Party.

He was also the President, Dumb Friends League and Honorary Counsel to the Society for the Prevention of Cruelty to Animals.