Ditches were an obvious obstacle to tanks. During the First War some British trenches were dug especially wide to act as barriers to tanks. Manual of Field Engineering 1925 states that a ditch 10 ft wide and 6 ft deep would make an effective obstacle while the 1936 Manual gives examples of a 9 ft ditch or an 8ft ditch with one vertical (or alternatively a 2:1 slope) side.
The standard design of ditches used for Home Defence probably originated from Southern Command following experiments held in the autumn of 1940 (for e.g. at Sutton Veny on Sept 14th). Following these trials the two way ditch became standard in Southern Command.
The design of standard ditches can be found in the manuals of the time for e.g. 1943 Field Engineering Military Training Pamphlet No 3 Part III:
1) V Ditch – not as effective as a ditch with a vertical face but did not need revetting.
2) One-way ditch – tank proof in one direction only – the tank could back out.
3) Two-way ditch – tank proof in both directions but requires more time to construct.
Anti-tank Ditches, Military Training Pamphlet No 30 Part III, Obstacles
The recommendation was to dig ditches in straight lengths of about 400 to 600 yards in a zig-zag trace so that enfilade fire can be organized along them.
The main period of ditch construction was from autumn 1940 to spring 1941 – in October 1940 there were 320 excavators at work in Eastern Command. Ditches were dug to improve the obstacles guarding the main routes inland from beaches and some towns were given all round ditch defence (e.g. Lowestoft and Aldeburgh). Some planned ditches were never dug (e.g. a planned ditch to run around Leiston). A ditch at Westleton Walks/Dunwich Heath would appear to have been sited next to a natural steep slope to enhance the obstacle. The Eastern Command Line relied almost entirely on natural obstacles or railway cuttings/embankments.
Top right and left: Ruston Bucyrus fitted with back actor
equipment. Bottom left: Ruston Bucyrus fitted with drag
line equipment. A back actor could excavate approx 70
cubic yards per hour while a drag line up to 85 cubic
yards per hour (in sandy soil). However the drag line
required a great deal of skill to operate. The drag line
would have been especially useful for widening existing
water courses to form anti-tank ditches.
The Ruston Bucyrus was the excavator normally used by
British forces though no doubt in 1940/41 any contractor
with any make of machine was u
Some contractors noted as being employed on the construction of anti-tank ditches included the Ministry of Transport (Corton ditch), Messrs. French (Thorpeness and Bawdsey ditches) and the East Suffolk Catchment Board in the Felixstowe area.
One of the easiest and quickest ways to construct ant-tank ditches was to widen existing drainage ditches and such work was carried out on virtually all of Suffolk’s coastal marshes. Some marshes were also permanently flooded for example at Walberswick and Minsmere while provisions were made to flood others during invasion (e.g. Minsmere Levels south of the ruined chapel).
Today a good example of a two way ditch can be seen at Aldringham Walks and many of the widened ditches on the coastal marshes are still obvious compared to other ditches.
Two-way Anti-tank Ditch, Aldringham Walks. The profile of the ditch
suggests it may have been excavated by drag line.
Manual of Field Engineering (All Arms), 1925
Experiments with anti-tank obstacles, WO199/1722 TNA
Military Training Pamphlet No 30 Part III Obstacles, War Office, 1943
Manual of Field Engineering (All Arms) Vol II 1936
Guide to Mechanical Equipment, B.N.A.F., 1944
RE Pocket Book, No.5C, Earthmoving Plant, WO 1951