When J.R. Jayewardene became the first Executive President of the country, he appointed Premadasa as the Prime Minister on 23 February 1978. Premadasa began to define the new role of the Prime Minister under an executive president. He took residence at Temple Trees, retained the use of the The Lodge for the prime minister and established a new prime minister's office at Sirimathipaya. He began representing Sri Lanka internationally, having led the Sri Lankan delegation to the Commonwealth Heads of Government Meeting in 1979, where he secured British funding for the construction of the Victoria Dam. He headed the Sri Lankan delegation to the United Nations General Assembly in 1980 where he addressed the general assembly.