Complex sentence: The success of the radio series prompted the BBC to acquire the rights to the original TV episodes from PolyGram, and from 20 September 1991, "Thunderbirds" was networked (broadcast simultaneously to all regions) on BBC 2.
Split into simpler sentences: The success of the radio series prompted the BBC to acquire the rights to the original TV episodes from PolyGram. From 20 September 1991, "Thunderbirds" was networked (broadcast simultaneously to all regions) on BBC 2.