Complex sentence: In World War I Trentham was bombed by Zeppelin'L 21'; and during the Second World War, Trentham Hall, within the Gardens, was used as a clearing house by the Bank of England.
Split into simpler sentences: In World War I Trentham was bombed by Zeppelin'L 21'. During the Second World War Trentham Hall was used as a clearing house by the Bank of England.