Complex sentence: Leader Stirling first experience with politics was at the age of 18 when during a school debate he made a "burlesque political speech" which prompted his schoolmaster to jokingly say that "Stirling will undoubtedly become a politician".
Split into simpler sentences: Leader Stirling first experience with politics was at the age of 18. During a school debate he made a "burlesque political speech" which prompted his schoolmaster to jokingly say that "Stirling will undoubtedly become a politician".