Then he joined the 1948 radio play Vinoda Samaya along with Joseph Seneviratne, Vincent Weerasekera, Harriet Suraweera, Pitipana Silva and Sisira Kumara Manickaarachchi.
[2] In 1952, Bertie was anointed as Sri Lanka's first amateur comedian in the Bushels Coffee program hosted by Thevis Guruge.
In 1954, Gunathilake along with his close friends Annesley Dias and Samuel Rodrigu presented the comic program Vihilu Thahalu for Radio Ceylon under the guidance of H.D.
[8] In later years, many more characters were included in the program such as Gemunu Wijesuriya, Joseph Seneviratne, Alfred Perera and Mercy Edirisinghe.
[3] Once, Gunathilake pretended a role "Two Tone" as a schoolboy, wearing a pair of shorts, a teat in his mouth, a bottle of water, a pencil and a book in the popular comedy sitcom Vinoda Samaya.
[4][7] His maiden cinema appearance came through 1951 film Banda Nagarayata Paminima directed by Raja Wahab Kashmeer.
[2] Then he acted in many supportive comedy roles in popular commercial films such as Pem Mal Mala, Palama Yata, Deviyani Sathya Surakinna, Mana Mohini and Somy Boys.
[3] In 2013, his biography Sadadaraneeya Berty written by Kingsley Wijesundara was launched along with Gunathilake's 89th birthday party at his residence at Godakawela, Kosnathota.
[9] On 13 November 2013, The Ministry of Cultural Affairs conferred the "Desha Nethru" Award at the National Literary Arts Festival.