The Bulwark: a Civil War fieldwork and World War II gun emplacement, 150m north of Earith Bridge


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Date of most recent amendment:


© Crown Copyright and database right 2021. All rights reserved. Ordnance Survey Licence number 100024900.
© British Crown and SeaZone Solutions Limited 2021. All rights reserved. Licence number 102006.006.
Use of this data is subject to Terms and Conditions.

The above map is for quick reference purposes only and may not be to scale. For a copy of the full scale map, please see the attached PDF - 1013282.pdf

The PDF will be generated from our live systems and may take a few minutes to download depending on how busy our servers are. We apologise for this delay.

This copy shows the entry on 13-Apr-2021 at 06:38:58.


The building or site itself may lie within the boundary of more than one authority.

Huntingdonshire (District Authority)
National Grid Reference:
TL 39255 75008

Reasons for Designation

English Civil War fieldworks are earthworks which were raised during military operations between 1642 and 1645 to provide temporary protection for infantry or to act as gun emplacements. The earthworks, which may have been reinforced with revetting and palisades, consisted of banks and ditches and varied in complexity from simple breastworks to complex systems of banks and inter- connected trenches. They can be recognised today as surviving earthworks or as crop- or soil-marks on aerial photographs. The circumstances and cost of their construction may be referred to in contemporary historical documents. Fieldworks are recorded widely throughout England with concentrations in the main areas of campaigning. Those with a defensive function were often sited to protect settlements or their approaches. Those with an offensive function were designed to dominate defensive positions and to contain the besieged areas. There are some 150 surviving examples of fieldworks recorded nationally. All examples which survive well and/or represent particular forms of construction are identified as nationally important.

The fieldwork near Earith is very well preserved, retaining numerous details illustrating the style of defence. Only a small part of the earthworks (at the southern corner of the monument) have been significantly disturbed, and here the ditch will survive as a buried feature. The banks, parapets and bastions contain details of their construction, and the ditches contain shallow deposits of waterlogged silts which both indicate the transient use of the site, and provide conditions suitable for the preservation of organic and inorganic artefacts from the period of occupation.

The Bulwark is amongst the most elaborate fortifications in England to have survived from the Civil War. It demonstrates clear influences of contemporary continental military design and shows how these ideas were adapted in the English context. The Earith Bulwark demonstrates the importance of the Earith crossing during the Civil War as part of the military frontier surrounding the Isle of Ely and, together with a number of other fortifications in the region (both in similar rural locations and in the main towns), illustrates the variety of methods adopted for the defence of the Eastern Association. The survival of the two rectangular outworks demonstrate the garrison's reliance on both the adjacent means of communication.

The World War II gun emplacement is also a very well preserved and unusual survival, retaining the principal elements of its design. The use of the dual purpose Alan-Williams turret in this location illustrates its twin purposes: a defence against the threat of German invasion along the Ouse valley, and the more immediate problems posed by the vulnerability of the Earith flood defences from the air.


The Civil War fieldwork known as The Bulwark is situated to the east of Earith, within a narrow strip of land (the Hundred Foot Washes) which separates the Old and New Bedford Rivers, both of which join the Great River Ouse some 150m to the south.

The Bulwark was strategically placed to command an important river crossing at the western end of the fen causeway which linked Huntingdon to the the Isle of Ely; and to control traffic on both the River Great Ouse, and the earlier of the two artificial navigations (the Old Bedford River), constructed by the engineer Vermuyden in the 1630's. The monument includes the fieldwork with its square inner enclosure, corner bastions, perimeter defences and outworks; and a small steel-domed gun emplacement positioned within the earlier fortifications during World War II.

The central enclosure is raised about 0.7m above the surrounding ground level, measures approximately 60m square, and is located within the angle between the the River Great Ouse and the Old Bedford River which lies c.300m to the south west. The enclosure is surrounded by an earthen rampart and parapet, which varies between 0.5m and 1m in height, and between 4m and 10m in width. The parapet would originally have had a near vertical inner face supported by timber work and pierced by gun loops, but has since subsided to a rounded profile. It continues around each of the four, lozenge-shaped bastions which form diagonal projections at the north, south, east and west corners, with a single gap or entrance in the centre of the south east side. The bastions each extend for about 30m and measure approximately 20m across the widest parts. These served as cavaliers (artillery platforms) with a wide range of fire, and allowed close quarter defence for the ramparts to either side. This central stronghold, or sconce, is surrounded by a broad ditch with steep sides and a flat base. This measures about 17m in width, descending to about 3m below the parapet, and may originally have been strengthened by a fringe of sharpened poles inserted in the inner face. Sample excavation across the northern bastion in 1906 demonstrated that the profile of the inner fortifications resulted from a single phase of construction, with the upcast gravels forming the inner rampart, clad with heavy clay from the base of the ditch. The 1906 excavation also revealed a shallow deposit of dark alluvial silts in the bottom of the ditch which indicate that when freshly cut it contained standing water. The ditch is flanked by an outer bank rising in two stages, the outer stage forming a further parapet or breastwork, with a rifle platform or covered way behind. The bank is generally 6m-8m wide and 1m high, with the breastwork covering about half its width and raising its height by approximately 0.8m. The breastwork is also thought to have subsided since the collapse or removal of an inner palisade, but even in its original condition, it would have been lower than the firing height from the parapet within the sconce. The covered way provided access to two bastions in the outer defensive circuit, located in the centre of the north eastern and south eastern arms. The former is a roughly triangular protrusion extending for c.6m beyond the line of the bank. The latter is similar in size but with a more rounded appearance. Both have narrow gaps, or sally ports, in the breastwork; and square platforms behind, providing mustering points or further gun emplacements. The north eastern platform is linked to the central enclosure by two narrow causeways across the ditch. The south eastern platform is approached by a square projection from the inner parapet which extends about half way across the ditch, thought to indicate the position of a short drawbridge. Except on these bastions, the outer face of the breastwork forms part of a single slope (or glacis), with an unrestricted field of fire, leading into the inner scarp of an external ditch. This ditch is generally 3m in width and c.0.7m deep, having been partially infilled by silts deposited during the seasonal flooding of the washes. It remains visible around the full circuit of the fortifications except at the tip of the southern corner bastion where the earthworks have been reduced and the ditch largely infilled. Along the north eastern arm it has been partially recut by a later field drain. On the north western side of the fort, the perimeter ditch extends to form a rectangular enclosure which projects for about 100m towards the Old Bedford River, providing a fortified approach or outwork. The outwork measures approximately 40m in width (the same width as the inner parapet between the corner bastions), and has indications of two further lozenge-shaped cavaliers at the far corners. Slight traces of an extension to the outer breastwork extend down each side of the outwork leaving a gap at the approach to the sconce, where a large, squared projection from the outer bank into the main ditch is thought to represent the footings for a drawbridge. A similar outwork extends from the south west side of the fort, continuing for about 150m towards the road on the north bank of the River Great Ouse. This also is accompanied by a gap in the breastwork and a square bridgehead on the outer bank of the inner ditch. Two major entrances to a fortification of this type is an extremely unusual arrangement, perhaps explained by the garrison's reliance on reinforcements and supplies by both road and river.

The Bulwark was constructed by Parliamentarian forces between 1643 and 1645, during the first stage of the Civil War. It is believed to be the work of two English engineers, Richard Clamp and Captain John Hopes, although the design is largely based on the Dutch school of military fortification, then dominant on the continent. The precise date of construction is unknown. At the onset of the war Huntingdonshire formed part of the Midlands Association of Parliamentarian counties, becoming a frontier county of the Eastern Association shortly after it was formed in 1643. The Eastern Association led by Oliver Cromwell (amongst others) initially took a defensive stance, concentrating on the fortification of Cambridge and the control of major communication routes which, in the fens, largely consisted of the principal causeways and navigations. The Bulwark is unlikely to have been constructed prior to this period since, in the previous year when the Queen's troops and forces under the Marquis of Newcastle threatened the area, an officer named Tyrell Jocelyn reported that the bridge at Earith (Hermitage Pass) could be held for a week; an extremely low estimate if the fortifications were in place. Early in 1643 Cromwell embarked on a strategy to consolidate the Association's military frontier; first securing the Royalist ports of Lowestoft and King's Lynn, then moving on to take Peterborough and finally Crowland, the last Royalist outpost in the fens. In May, there was a Royalist rebellion on the Isle of Ely, which was eventually suppressed by troops from Cambridge. However, this rebellion demonstrated that the Isle would be readily defendable by a larger force should it fall to the opposition. The major approaches from the north and west were therefore strengthened, with garrisons at Wisbech and Earith, perhaps involving the construction of the Bulwark, and possibly also the large pentagonal sconce at Horsey Hill, near Peterborough. If these fortifications were not erected in response to this crisis, they may well have been built in the following year after the Parliamentarian defeat at Cropredy Bridge, near Banbury, when the Association was ordered to take additional defensive measures. A further defeat at Lostwithiel in Cornwall in October 1644 resulted in Cromwell marching his forces west, leaving the eastern counties short of troops. Parliamentarian fortunes improved after the battle of Naseby in August 1645. However, in retreat from the battle, Charles I turned south east briefly, taking first Stamford then Huntingdon. Although this occupation was short lived the aftermath saw renewed fortification of all the Ouse crossings, and was perhaps the last occasion on which the Bulwark might have been built.

As far as the fens were concerned this was the end of the first phase of the war, the Bulwark, like many other East Anglian fortifications, never having seen action. The second phase saw far less activity locally, the only major action in the area being a provincial uprising in Colchester in 1648. The small structure located on the southern, inner bastion is an unusual form of gun emplacement dating from World War II, known as the `Alan-Williams' turret. It consists of a rotating steel dome 1.5m in diameter, set over a concrete lined pit with a entrance passage to the west. The dome contains space for two men, one to rotate the upper section, the other to operate a machine gun (since removed). The gun could be mounted through a square aperture in the side of the dome, or a circular aperture above. It was intended both for ground defence, covering the embankment of the New Bedford River, and against aerial attacks aimed at the bridges and sluices to the south. It is not known if it was ever used in action. All fences, fence posts and gates are excluded from the scheduling, although the ground beneath these features is included.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.


The contents of this record have been generated from a legacy data system.

Legacy System number:
Legacy System:


Books and journals
Darby, HC, The Changing Fenland, (1983), 76-77
Holmes, C, The Eastern Association in the English Civil War, (1974), 73
Kingston, A, East Anglia and the Great Civil War, (1902)
Morgan, K O (ed), The Oxford History of Britain, (1989), 675
Osborne, M, Cromwellian Fortifications in Cambridgeshire, (1990)
Shirer, W L, The Rise and Fall of the Third Reich, (1969), 914
Wickes, M, A History of Huntingdon, (1985)
Kent, P, 'Fortress' in East Anglian Fortifications in the Twentieth Century, , Vol. 3, (1989), 43-57
Keynes, G L, Evelyn White, H G, 'Proceedings of the Cambridge Antiquarian Society' in Excavations at Earith Bulwarks, , Vol. 12, (1908), 277-61
Saunders, A D, 'Archaeological Journal' in Proceedings, , Vol. 124, (1967), 222-3
report on gun emplacement (SMR 1780a), Wyatt, G, Earith Bulwark, (1980)
Text and plans, RCHM(E), Inventory of Historic Monuments, Huntingdonshire, (1926)
Undated, lecture notes (Cambs SMR), Baggs, T, The Civil War in East Anglia, (1980)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

Your Contributions

Do you know more about this entry?

The following information has been contributed by users volunteering for our Enriching The List project. For small corrections to the List Entry please see our Minor Amendments procedure.

The information and images below are the opinion of the contributor, are not part of the official entry and do not represent the official position of Historic England. We have not checked that the contributions below are factually accurate. Please see our terms and conditions. If you wish to report an issue with a contribution or have a question please email [email protected].