Churchill Barrier No. 3

Churchill Barrier No 3, about 420m long, is part of a group of four 'Churchill Barriers' built between 1940 and 1944 to link islands at the eastern side of Scapa Flow. The barriers are solid causeways that prevent access from the east into the four channels leading to Scapa Flow, the main British naval base during the Second World War. The scheme was designed and supervised by Sir Arthur Whitaker, Civil Engineer-in-Chief of the Admiralty. The contractors were Balfour Beatty & Co Ltd. Italian prisoners of war who were interned at Lamb Holm formed part of the workforce that made the concrete blocks and built the structure.

In accordance with Section 1 (4A) of the Planning (Listed Buildings and Conservation Areas) (Scotland) Act 1997 the following are excluded from the listing: concrete edge beam, crash barriers and modern road surfacing.

The defensive barriers were constructed to prevent ships and particularly submarines from entering Scapa Flow from the east, but they also provide road access southwards from Mainland to South Ronaldsay. Barrier 3 links Glimps Holm and Burray. Although conceived and built at a time of national crisis, their lasting role has been as causeways and roads linking islands together.

Barrier 3, like the other barriers, has a base built using bolsters, wire cages or baskets that were filled with broken rock and then dropped into the water of the channel. Most of this deep structure is underwater. A road carriageway formed from dumped aggregate and horizontally laid concrete blocks overlies the causeway base. Five ton cast concrete blocks placed in varying positions on either side of the barrier at angles help to protect the causeway core and prevent the tide from overtopping the carriageway. In total, all four barriers required about 250,000 tons of stone rubble and 66,000 concrete blocks. The barriers now carry the A961 road south to South Ronaldsay. The barriers are numbered from north to south.