 Several perceived weaknesses of the 1947 Soulbury Constitution, however, eventually led to calls for a replacement, particularly from nationalists and the Left, the Lanka Sama Samaja Party's Colvin R. de Silva being a central figure in the movement.The United Front, led by Sirimavo Bandaranaike's Sri Lanka Freedom Party, won the 1970 general election with a two-thirds majority.As Prime Minister, Bandaranaike convened a number of committees to draft a new constitution, including a drafting committee chaired by the Minister for Constitutional Affairs, Colvin R. de Silva.