Whilst studying law, de Silva joined Associated Newspapers of Ceylon Limited, popularly known as Lake House, in 1954 as a part-time parliamentary reporter.[3] He became a permanent member of staff at Lake House in 1960 and in 1965 he was appointed deputy editor of The Observer.[3] In 1970 he was appointed editor of the Ceylon Daily News, the country's leading English-language daily newspaper.[3] He was appointed editor-in-chief of the Lake House group of newspapers in 1972.[3] Lake House was nationalised in 1973 and in 1976 de Silva was sacked by the government.[3] He became editor-in-chief of the Times of Ceylon group of newspapers in 1976.[3] The Times of Ceylon group was itself nationalised in 1977 and in 1978 de Silva was sacked by the government again.[3] De Silva founded the Lanka Guardian journal in May 1978 which he continued to edit until his death.[3] During his tenure at the Lake House, Mervyn worked alongside the likes of Willie de Alwis,[8][9]Premil Ratnayake,[10]D. B. Dhanapala[11] and Christie Seneviratne.[12]
He was involved in the establishment of the Council of World Affairs with Major General Anton Muttukumaru and initiated the Foreign Affairs Advisory Group along with Gamani Corea, Lakshman Kadirgamar, Stanley Jayewardene and Gamini Wijesinghe.
