Under Carrington's tutelage, Leach quickly elevated his play and became England's top player. By 1946, he achieved a world ranking. In 1947, he reached the semi-finals of the first post-war World Championships by beating Carrington in straight sets in the quarterfinals. He then lost a four-set match to eventual champion Bohumil Váňa of Czechoslovakia. In doubles, Leach and Carrington lost in the finals to Váňa and Adolf Slar. The following year, Leach reached the final sixteen of the World Championships before losing a five-set match to France's Guy Amouretti.