Admiralty scaffolding, also known as Obstacle Z.1, or sometimes simply as beach scaffolding [1] or anti-tank scaffolding, [2] was a British anti-tank and anti-boat obstacle design made of tubular steel. It was widely deployed on the beaches of southern England, eastern England and South West England during the British anti-invasion preparations of World War II, [3] [4] though scaffolding was also used, but more sparingly, inland. [5]
Of a number of similar designs, obstacle Z.1 was by far the most common. This design comprised upright tubes 9 feet (2.7 m) high and 4 feet 10 inches (1.5 m) apart, connected by up to four horizontal tubes. Each upright was braced by a pair of diagonal tubes, at approximately 45°, to the rear. [6] 20-foot (6 m) wide sections were assembled and carried to the sea to be placed in position at the half tide mark as an obstacle to boats. [6]
However, trials found that a 250-ton barge at 5+1⁄2 knots (6.3 mph; 10.2 km/h) or an 80-ton trawler at 7+1⁄2 knots (8.6 mph; 13.9 km/h) would pass through the obstacle unimpeded, and a trawler easily pulled out one bay with an attached wire rope. [7] Tests in October 1940 confirmed that tanks could only break through with difficulty. As a result, Z.1 was adopted as an anti-tank barrier for beaches thought suitable for landing tanks. As an anti-tank barrier, it was placed at or just above the high water point [6] where it would be difficult for tanks to gain enough momentum to break through. In some places, two sets of scaffolding were set up: one in the water against boats, and one at high water against tanks. [8]
The problem of securing the barriers on sand was overcome by Stewarts & Lloyds' development of the "sword picket"– This device was later known at the Admiralty as the "Wallace Sword". [7] [9]
Barriers ranging in length from a couple of hundred feet to three miles were constructed, consuming 50% of Britain's production of scaffolding steel [6] at an estimated cost of £6,600 per mile [6] (equivalent to £460,000 today [10] ). Despite this, many miles of Admiralty scaffolding were erected using more than 15,000 miles (24,000 km) of scaffolding tube. [9]
After the war, the scaffolding obstructed swimmers, [11] [12] and was subsequently removed for scrap. Remaining traces are very rare, but occasionally revealed by storms. [13] [14] [15] [16] [17]
