Complex sentence: Educated at Kingston Grammar School he joined the Royal Air Force in 1936, and spent World War II in Europe, North Africa and South East Asia: he was mentioned in despatches twice.
Split into simpler sentences: Educated at Kingston Grammar School he joined the Royal Air Force in 1936. He joined the Royal Air Force in 1936 and spent World War II in Europe, North Africa and South East Asia: he was mentioned in despatches twice.