off in this way. James Campbell Clouston, pier master on the east mole, organised and regulated the flow of men on that site. Churchill Barriers The Churchill Barriers are a series of four causeways in the Orkney Islands with a total length of 1.5 miles (2.4 km). They link the Orkney Mainland in the north to the island of South Ronaldsay via Burray and the two smaller islands of Lamb Holm and Glimps Holm. The barriers were built in the 1940s as naval defences to protect the anchorage at Scapa Flow. They were commissioned following the sinking of HMS Royal Oak in 1939 by German U-boat U-47 which had penetrated the existing defences of sunken blockships and anti-submarine nets. The barriers now serve as road links, carrying the A961 road from Kirkwall to Burwick. Heptastadion Notable in antiquity was the Heptastadion, a giant mole built in the 3rd century BC in the city of Alexandria, Egypt to join the city to Pharos Island where the Pharos lighthouse stood. The causeway formed a barrier separating Alexandria's oceanfront into two distinct harbours, an arrangement which had the advantage of protecting the harbours from the force of the strong westerly coastal current. The Heptastadion is also believed to have served as an aqueduct while Pharos was inhabited, and geophysical research indicates that it was part of the road network of the ancient city. Silting over the years resulted in the former dyke disappearing under several metres of accumulated silt and soil upon which the Ottomans built a town from 1517 onwards. Part of the modern city of Alexandria is now built on the site. English Tangier When the Kingdom of England acquired the north African city of Tangier as English Tangier in 1661, the English began building a mole to improve the harbour. The mole was planned to be long and cost £340,000, and the improved harbour was to be long, deep at low tide, and capable of keeping out the roughest of seas. Work began on the mole in August 1663 and continued for some years under a succession of Governors. With an improved harbour the town would have played the same role that Gibraltar later played in British naval strategy. However, Parliament expressed concern about the cost of maintaining the Tangier garrison, and by 1680 King Charles II had threatened to give up Tangier unless the supplies were voted for its