Complex sentence: The new chain, designed by engineer Captain Thomas Machin, could have theoretically been lowered in order to let friendly ships sail down the river, but the chain was never tested, and was later discarded after the war.
Split into simpler sentences: The new chain, designed by engineer Captain Thomas Machin. The chain could have theoretically been lowered in order to let friendly ships sail down the river, but the chain was never tested, and was later discarded after the war.