Complex sentence: There has never been a Bentley model known as the'Mark IV': neither from the'old' W.O. Bentley firm, nor from Rolls-Royce after the takeover of Bentley Motors in 1931.
Split into simpler sentences: There has never been a Bentley model known as the'Mark IV'. Not by the'old' W.O. Bentley firm, or by Rolls-Royce after the takeover of Bentley Motors in 1931.