Read this: The 1-mile-long (2 km) Breakwater in Plymouth Sound was designed by John Rennie in order to protect the fleet moving in and out of Devonport; work started in 1812. Numerous technical difficulties and repeated storm damage meant that it was not completed until 1841, twenty years after Rennie's death. In the 1860s, a ring of Palmerston forts was constructed around the outskirts of Devonport, to protect the dockyard from attack from any direction.

Who was the designer of the Plymouth Sound Breakwater?
What is the answer? (If it cannot be answered, return "unanswerable")
John Rennie