Complex sentence: The camp continued to be enormously successful throughout the 1970s but, on 29 October 1986 Butlins announced that Barry Island holiday camp would have no place in the company's future and would close after Christmas.
Split into simpler sentences: The camp continued to be enormously successful throughout the 1970s. But, on 29 October 1986 Butlins announced that Barry Island holiday camp would have no place in the company's future and would close after Christmas.