 Complete the following phrase:  By 1947, Fred Davis was deemed ready by his brother to become world champion, but lost the world final to Walter Donaldson. Fred Davis and Donaldson would contest the next four finals. After the abandonment of the World Championship in 1953, with the 1952 event boycotted by British professionals, the World Professional Match-play Championship became the unofficial world championship. Fred Davis won the tournament every year from 1952 to 1956, but did not enter the 1957 event. John Pulman won the 1957 event and was the most successful player of the 1960s, won the event seven times between April 1964 and March 1968 when the World Championship was contested on a challenge basis. This winning streak ended when the tournament reverted to a knockout format in 1969. Ray Reardon was the domit force in the 1970s, winning six world titles 1970, 19731976, and 1978, and John Spencer won three 