The Enigma that is Raw Dykes Scheduled Monument
Two banks
It’s likely that few people notice the earthworks that occupy a wedge of land to the south of the city centre. This wedge has the Aylestone Road to the south-east, a disused railway line to the south-west, and waste land, the site of an electricity power station, on the third side.
These surroundings form a far from ideal backdrop to a scheduled monument. Nevertheless, when seen close to, the earthwork is quite impressive. The two banks run parallel for some 110 metres (ca.120 yards) in an approximately north east - south west direction, separated by a ‘U’-shaped depression some 6 metres (20 feet) wide and 2.5 metres (8 feet) deep. The western bank is the larger of the two; it is 17 metres (55 feet) wide and stands some 4 metres (13 feet) above the depression.
Once much larger
It’s probably difficult to appreciate today that this relatively short earthwork was once part of a much longer feature, but there is indisputable evidence that this was the case. When the famous antiquary William Stukeley visited the site in 1722, he made a number of sketches, one of which depicted the banks extending south for some considerable distance towards the village of Aylestone. Open the attachment below to see Stukeley's sketch. Some of these sketches appeared as engravings in the first volume of his first book Itinerarium Curiosum(1724), above a sketch map of the earthwork drawn by a Mr Roberts. Roberts’ map shows the earthworks extending for more than 550 metres (2000 feet) with an area of meadowland separating it from the River Soar to the east. Open the attachment below to see Mr Roberts' map.
Even in the late 18th century there was some uncertainty as to the exact length of the surviving monument. In 1795 John Nichols, the local antiquary, told us of two surveys of the earthworks. In 1752 the first of these calculated the length as 634 yards, 2 feet (580 metres). Thirty-five years later, a second survey arrived at a figure of 667 yards (610 metres). Nichols also describes how 163 paces of the eastern bank had been ‘subdused’ [ie removed].
The 19th and 20th centuries witnessed much more extensive damage to the monument. A document of 1804 records that sections had been levelled to make way for a turnpike road and a racecourse. The best indication of the condition and extent of the surviving earthwork, however, comes from the Ordnance Survey (OS) maps. The First Edition OS map of 1885 shows the west bank extending some 610 metres (670 yards) to the north of the railway, but the east bank is much reduced, and only extends for some 330 metres (360 yards).
By the time that the Second Edition OS map was surveyed in the first decade of the 20th century the west bank had been dramatically reduced to a mere 330 metres (360 yards) whilst the east bank had been further eroded to down to 300 metres (329 yards). The reason for this dramatic reduction was the establishment of one of the early County Cricket Grounds at the northern end of the surviving earthworks. The accounts of the groundsman of the time relate how a length of the western earthwork was removed, and the spoil dumped on the eastern margin of the ground.
By the time the Third Edition map was being surveyed in the second and third decades of the century the surviving monument had been reduced yet again to more or less the size of today’s scheduled area. There was increasing demand for access to the land to the west of the Aylestone Road. The meadowland closest to the Soar was becoming industrialized, whilst the area immediately to the west of the road were used as the County Showground. By the middle of the 20th century the County Showground had moved across the road, and all of the area between the former Filbert Street football ground and the railway had become an electricity power station.
Although we have good evidence for what happened to the banks to the north of the scheduled area in recent centuries, we know far less about the extent of the banks to the south of the scheduled area. Stukeley’s engraving depicted the banks running towards Aylestone village, but did not show how far they extended. Unfortunately there are no maps showing the earthworks extending any further south than the disused railway. All we know for certain is that the railway was built in the late 1840s, and that the area immediately to the south of the line was developed as a gas works in the 1870s. These two developments are likely to have removed all surface traces of the banks that might have run to the south of the scheduled area.
We also know far less about the extent of the earthworks prior to the 18th century. Although there are one or two documentary clues that originally it stretched even further north, no trace of Raw Dykes has ever been recognised in archaeological excavations that have taken place to the north of Aylestone Road.
The Original Function
Several suggestions have been put forward as to the original function of Raw Dykes, but a couple of them can be rapidly dismissed:
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A Defensive Boundary: In his work Britannia, published in 1588, William Camden suggested that the earthwork was a defensive boundary. Such long defensive earthworks are found in other parts of the country, such as the Devil’s Dyke in Cambridgeshire, Wat’s Dyke in Herefordshire, Wansdyke in Wiltshire, and Offa’s Dyke on the English-Welsh border. However, these long defensive earthworks invariably take the form of a single bank with an external ditch, rather than the two banks.
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A Racecourse: Stukeley’s belief was that the banks formed one of the sides of a racecourse. This suggestion probably says more about the preoccupations of a country gentleman in the early 18th century than it does about Raw Dykes.
A Link with Roman Leicester: Other observers pointed out the proximity of Raw Dykes to the Roman town of Leicester the southern defences of which lies some 1.5 km (1 mile) to the north of the scheduled monument. They suggested that the two had to be linked in some way. Open the attachment below to see an illustration of this.
Problem: There was one difficulty with any theory linking the earthwork with Roman Leicester. This is that all the maps and surveys of the site from the 18th century onwards indicate that Raw Dykes ran in a south west-north east direction. If the earthwork continued on this course, it would have run well to the east of the Roman town. In the absence of archaeological evidence that Raw Dykes turned to the west there needed to be some other evidence to indicate that this was the case.
Documentary Evidence: Fortunately there are written clues that Raw Dykes did not continue northwards on the same course as the one shown on the early OS maps.
Camden states that Raw Dykes ‘are not five-hundred paces from the South Gate’. Although it is not clear exactly what he meant by this, it suggests both that Raw Dykes diverted from the course it takes further south, and that direction took it close line of the southern defences of the Roman town.
Notes made by a Royalist officer in the Civil War support this testimony. Writing in 1645, when the Royalists were besieging Leicester, the officer indicates that the Royalist artillery was mounted on one of the banks. This gun platform is unlikely to have been more than a few hundred yards from the city defences.
Original Function?
So there is good reason to believe that Raw Dykes are associated with Roman Leicester, but there is some debate as to what function the earthwork served:
A Canal?
One school of thought suggests that the banks served to retain water for a canal that ran from a location to south of the city. According to this hypothesis, a canal was built to carry stone from the granite outcrops close to the River Soar 6.5 km (4 miles) upstream of Leicester. Features seen on aerial photographs close to the river to the south of the earthwork are taken to be traces of this canal. Although this idea cannot be totally rejected, there are powerful arguments against it:
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The Romans did build canals, but mainly for drainage or irrigation purposes, or to provide navigation in silted harbours. The only Roman canals we know of in Britain were dug to drain the Fens.
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Only on rare occasions did the Romans build canals to carry goods. These tend either to link parts of major navigable rivers (such as the lower Rhine) or else to supply the army on a major campaign. No other Roman cities, even cities far larger than Roman Leicester, had canals just to carry building materials. The effort of digging a canal would probably have been greater than hauling the stone overland.
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Each of the features seen on aerial photographs can be explained in terms of former natural river channels, drainage channels or track-ways.
An Aqueduct?
This is by far the most likely suggestion as to the function of Raw Dykes. Most towns and cities in the Roman Empire had supply of clean water supplied via an aqueduct. Larger cities, such as Rome, often had several aqueducts. Invariably this water was drawn from a nearby spring or stream, rather than the local river. Presumably this was because river water was rarely clean enough.
There is, however, no absolute proof that the earthworks are the remains of an aqueduct. When she was excavating the Roman baths in the 1930s, Kathleen Kenyon cut a trench across the surviving earthwork. Open the attachment below to see an illustration of the section. She found that there was a ‘V’-shaped slot between the two banks and recovered what she believed to have been Roman pottery from one of the banks. This might have settled the matter once and for all if it were not for:
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Some of the pottery that she believed to have been Roman was probably mediaeval.
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The surveying she carried out which she believed showed that the channel between the banks to have been at too low a level to feed water all the way to the Roman town. She suggested that the earthwork was the work of an ‘incompetent provincial engineer’, but this is an satisfactory explanation because there were plenty of competent Roman engineers around who could have made an effective aqueduct, and if there had been a mistake in construction the Romans would have rectified it rather than abandoning the project.
Even though absolute proof that Raw Dykes was an aqueduct was not forthcoming, the theory still stands up. Kenyon’s surveying technique has been called into question and there are many ways in which mediaeval pottery can be introduced into a Roman earthwork. Recent fieldwork has demonstrated that a similar set of two banks in Dorset was a part of an aqueduct supplying water to Roman Dorchester.
A Water Source?
If Raw Dykes was an aqueduct, what was the source of the clean water? The most likely source is the stream known as the Saffron or Knighton Brook which flows west into the Soar some 300 metres (330 yards) to the south of the scheduled monument. Today this brook is a canalised stream running through suburbs, allotments and the former gasworks. But in the Roman period the stream would have flowed across open country could have been dammed to form a pond. More recent development will have removed all obvious traces of both dam and pond.
