Complex sentence: Perry was the first player to win a "Career Grand Slam" winning all four singles titles at the age of 26 which he completed at the 1935 French Open and remains the only British player ever to achieve this.
Split into simpler sentences: Perry was the first player to win a "Career Grand Slam", winning all four singles titles at the age of 26 which he completed at the 1935 French Open. He remains the only British player ever to achieve this.