Complex sentence: He graduated from Eton in 1940, spent a year at Oxford University and then was drafted into the army in 1942 until it was discovered he was suffering from TB at which point he was discharged and returned to London.
Split into simpler sentences: He graduated from Eton in 1940, spent a year at Oxford University and then was drafted into the army in 1942 until it was discovered he was suffering from TB. At which point he was discharged and returned to London.