Before revision: The barriers were built between May 1940 and September 1944, primarily as naval defences to protect the anchorage at Scapa Flow, but since 12 May 1945 , serve as road links between the islands.
After revision: The barriers were built between May 1940 and September 1944they primarily as naval defences to protect the anchorage at Scapa Flow, but since 12 May 1945 , serve as road links between the islands.