Complex sentence: He then taught French and German at Eton College for two years, afterwards becoming an MI5 officer in 1958; he ran agents, conducted interrogations, tapped telephone lines, and effected break-ins.
Split into simpler sentences: He then taught French and German at Eton College for two years, becoming an MI5 officer in 1958. He ran agents, conducted interrogations, tapped telephone lines and effected break-ins.