In 1988, PZPR Communist party leaders started negotiations with representatives of the then unofficial opposition. In the early months of 1989, as a result of the Round Table talks, an agreement was signed calling for partially free elections to the Parliament. The opposition was to have 35% of the seats in Sejm, and an entirely free election to Senate. The election held on 4 June 1989 brought a landslide victory to Solidarity. It was clear that the Communist Party would not be able to continue to govern in the face of such massive opposition from the people. Although the Parliament returned,  dubbed the "contractual Parliament", elected Gen. Jaruzelski President of the Republic, the office of Prime Minister was entrusted to a Solidarity candidate, Tadeusz Mazowiecki, who had been chief adviser to the Gdańsk strike committee in 1980. On 29 July 1989 the Parliament changed the country's name and constitution. The People's Republic of Poland became a thing of the past. The age of the Third Republic of Poland commenced. The events in Poland precipitated the fall of the entire Communist block. The Yalta arrangement collapsed. The Round Table compromise and peaceful transfer from the Communist system to a democratic system were possible thanks to the fundamental changes in the policy of the USSR, which in the period between 1986 and 1988 began to implement the ideas of glasnost and perestroika - political and economic openness to the outside world.