Complex sentence: However, the mole is passing substantive material, including American intelligence, to Polyakov, his handler, whilst Polyakov's material had just enough substance to persuade the CIA to share information with the British.
Split into simpler sentences: However, the mole is passing substantive material, including American intelligence, to Polyakov, his handler. The material Polyakov passes along had just enough substance to persuade the Americans to share information with the British.