Yes, before open tennis arrived, but the WCT only happened after open tennis. Sure in the late fifties, the Forest Hills Pro was the preeminent tennis tournament in the game, perhaps of all time. And Wembley was the premier tournament of 1952 and 1953 (although the Davis Cup was the most followed tennis event between 1946 and 1967). I think that in 1956, Wembley and Wimbledon were on a par. But once open tennis arrived, the grand slam had an enhanced and special meaning, even during the boycotted years.