A drawing of Admiralty scaffolding from 1940A section of Admiralty scaffolding prepared for testingExtant remains atSalthouse, North Norfolk, England.Exposed extant remains atWeybourne camp, NorthNorfolk, after the storm of October 2002
Of a number of similar designs, obstacleZ.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-tonbarge at5+1⁄2 knots (6.3 mph; 10.2 km/h) or an 80-tontrawler at7+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 thehigh 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 byStewarts & Lloyds' development of the "sword picket"– This device was later known at theAdmiralty 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]
Foot, William (2006).Beaches, fields, streets, and hills ... the anti-invasion landscapes of England, 1940. Council for British Archaeology.ISBN1-902771-53-2.
Ruddy, Austin (2003).British Anti-Invasion Defences 1940–1945. Official Handbook of the Pillbox Study Group. Historic Military Press.ISBN1-901313-20-4.
