Mathew joined the United National Party and was appointed its joint general secretary in 1956 and served until 1967, when he resigned after falling out with the party leader Dudley Senanayake.[3]
Mathew was expelled from the cabinet and the governing United National Party by PresidentJ. R. Jayewardene in 1984 after publicly criticising a conference called by Jayewardene to redress grievances of the Tamil minority.[15] Jayewardene's successor, Ranasinghe Premadasa, subsequently reinstated Mathew's party membership. He died of a heart attack on 17 October 1989.
Mathew was the author of the book Sinhalese! Rise to Protect Buddhism, which urged Sinhalese to "stand up for their rights and protect their values". He also issued a pamphlet Who is the Tiger, a collection of his inflammatory speeches made in 1979.
His son Nanda was also a member of the parliament[16] and later held several ministerial posts, including Minister of Sports and Youth affairs, under successive UNP governments.[1] He was later appointed by President Chandrika Kumaratunga and President Mahinda Rajapaksa as Governor of the Uva Province.