Building the Barriers The Churchill Barriers were built in response to the sinking in October 1939 of HMS Royal Oak by the German U47. Scapa Flow was the main base of the British Home Fleet in both World Wars and as such was poorly defended at the outset on both occasions. The Barriers now provide road access to Burray and Soth Ronaldsay, which in strong easterly winds can be hazardous due to large waves. Barrier #2 Barrier #1 Barrier #2 Barrier #2 Barrier #2 Barrier #3 Holm Sound aerial Kirk Sound tide Weddel Sound aerial blocks - detail blockworks blockworks cableway mast Kirk Sound masts opening in 1945 railway