Recent Archaeological Excavations at Brentford Lock from the Later Prehistoric to the 19th Century

by Lorraine Darton, Brentford & Chiswick Local History Journal 11, 2002

In May and June 2001 Pre-Construct Archaeology Ltd undertook an archaeological excavation at the former British Waterways Depot, at Brentford Lock. The excavation was commissioned by CgMs Ltd on behalf of their clients, St Georges, in advance of the re-development of a triangle of land between Brentford High Street and the River Brent at Brentford Lock. An archaeological evaluation was conducted at the site in Spring 1996 which determined that evidence of human activity spanning the Prehistoric, Roman, Medieval and Post-Medieval periods, had survived. During the 1960s redevelopment of Brentford, Roy Canham had recorded archaeological remains on the site, which he referred to as Sites 3 and 4. Accordingly, an open area excavation of 4 trenches on the site, was conducted in order to record the archaeological remains which would be destroyed by the new development.

The excavation produced evidence of activity at the site during the early Iron Age period (700-300 BC) in the form of pottery fragments found on the banks of a former channel of the Brent. Little subsequent activity prior to the Roman Conquest was recovered, when evidence in the form of pottery found in the base of a roadside ditch suggests that the major road from Londinium to Silchester was built between 45 and 70 AD. During the late 1st and 2nd centuries the roadside ditch was re-cut, and gravel surfaces, hearths, and pits, indicate the site was occupied during this period. The site appeared to have been abandoned by the end of the fourth century and there was apparently no further activity until field boundaries and drainage ditches were established in the Medieval period.

The rear walls of properties which had fronted onto the High Street, dated from as early as the 16th century. These properties formed strips of land running perpendicular to the High Street, in which rubbish pits, wells and soakaways were found. During the 17th to 19th centuries the site became increasingly developed and a Tannery was established along the banks of the River Brent. This article summarises  the main discoveries of the excavation, and discusses more fully the occupation of the site during the Roman period.

Geology & Prehistory
The site lies on thick deposits of the Langley Silt Complex (brickearth), overlying the Kempton Park Gravel Terrace of the River Thames. The thickness of the brickearth deposit as found on site and its imperviousness to water would have resulted in the site being poorly drained and difficult to till, with possible consequences for later land use.

A former river channel was found at the southern edge of Trench 3. The channel was probably the northern meander of the River Brent, curving around from SW-NE and then down NW-SE. The edges of the channel were filled by successive layers of sand and gravel overlain by silt, up to 1m thick. At Canham’s Site 2, he found the same channel south of the road at 141-147 High Street. Canham had problems in deciding the date of his Prehistoric pottery from Brentford and could not be sure as to whether it was Neolithic or Iron Age in date because of the apparent association with Neolithic flintwork. It now seems likely that his pottery also belongs to the early Iron Age and that the association with the flintwork was purely fortuitous.

It is possible to date the silting up of the Brentford Lock channel from the sherds of pottery found within the silt layers. One sherd had a finger impressed rim, suggesting an early Iron Age date (700-300 BC). Three rubbish pits were dug into the top of the channel fills and also contained pot sherds and fragments of burnt flints. This suggests cooking was taking place on the margins of the river and that there was an Iron Age settlement nearby.

The Brentford Lock excavation 2001: plan showing major Roman features

Roman activity
Roman activity began on the site very soon after the Roman Conquest in AD 43. An E-W aligned ditch running along the southern boundary of the site with Brentford High Street, was dug in the mid 1st century. This formed the northernmost ditch of the Roman road from Londinium to Silchester, which would place this stretch of the Roman road surface directly beneath the modern road. The roadside ditch was up to 1.2m deep and up to 4m wide.  Its large size, especially above where the former river channel lay, was probably due to the drainage problems on the site. The primary clay-ey fills of the ditch yielded pottery dating to between AD 45-70 mostly in Highgate Wood B ware, indicating the ditch was open in this period. The only other features on the site dating to this early Roman period were found in the east of the site; a small rubbish pit of about AD 50-60, which was overlain by a rammed gravel yard surface of AD 60-70.

The Roman road itself has been identified further to the east at 232-246 High Street, where a metalled gravel surface between 4 and 6m wide was recorded with two lateral roadside ditches. In the late 1st century this section of the road was extensively remodelled and widened to 12m across. This remodelling of the road was recognisable to the west at the Brentford Lock site, where in the late 1st century, the ditch was re-cut and widened to maintain efficient drainage. The primary fills of the re-cut roadside ditch yielded pottery dating to AD 70-100. This pottery includes fragments of wheel-turned jars and beakers from the Highgate Wood kilns, and the Colne Valley kilns near Staines and elsewhere in the Thames valley.

Also in the fills of the re-cut ditch were large quantities of iron slag from smithing hearth bottoms. Important Roman roads were metalled with iron slag brought from elsewhere, and this indicates some repair or resurfacing work took place when the ditches were recut, or as the edges of the road eroded, quantities of slag fell into the ditch.

Roman copper alloy dupondius of Domiitian AD 90-96

During the late 1st, 2nd and 3rd centuries the roadside ditch gradually silted up, and was no longer maintained. The pottery assemblage from this period included imported finewares such as fragments of beakers from south and central Gaul. Many metal objects were recovered from the ditch fills, presumably having been accidentally dropped by travellers and washed into the ditch.

Roman copper alloy mount cast in the form of a ram

The Roman coin assemblage fell into two groups; the late 1st century in the lower fills of the ditch, including a fine example of a dupondius of Domitian, dated to AD 90-96 whose lettering is unworn, suggesting it was not in circulation very long prior to its loss. Three coins recovered from the upper fills of the ditch dated to the 3rd century, one from the reign of Tetricus I, AD 270-273. Amongst the other objects discovered in the ditch were a Roman military belt mount, two decorative dress pins, a green glass bead, a finger nail cleaner, an ornately moulded knife handle, and a small mount cast in the form of a ram.

Smithing may have been taking place in the eastern part of the site in the 2nd century, as two smithing hearths were discovered. Nearby was a gravel surface and postholes which probably represented a wind break or similar structure, though they did not produce any discernible building plan. Smiths need to work in an environment with some shadow in order to see the subtle variations in the colour of the heated metal to check it has reached the correct temperature. Further evidence of second century smithing in this part of the site was provided by a large rubbish pit back-filled with iron slag from sixteen smithing hearth bottoms, and the presence of a well surrounded by several postholes and stakeholes on its edges. The posts and stakes may have formed a structure over the top of the well with a pulley system for collecting the water.

A 4th century N-S aligned ditch extended from the centre of the site down to the road, and may have formed a boundary. Evidence for late 4th century occupation on the site takes the form of rilled jar fragments from a beam slot, and from the uppermost fills of the roadside ditch. The sherds from the beam slot probably date the building’s demolition while the its postholes date to the late 3rd century, suggesting the building was occupied during the 4th century.

A more recently excavated site on the west bank of the River Brent at the Park Tavern, London Road, Brentford has produced evidence of Roman occupation to the south of the road. The earliest Roman activity dated to the 1st century consisted of a field boundary ditch and a gully. The next and most significant phase was occupation evidence dated to between the late 1st and 2nd centuries, consisting of post-built buildings, a hearth, and a cremation burial. The structures probably formed part of a Roman roadside ribbon development at the western edge of the Roman settlement of Brentford.

The buildings appear to have been abandoned at some time in the late 2nd century when the site became utilised as an external yard area. By the end of the late 3rd or early 4th century the yard surface had gone out of use, with a new ditch perhaps indicating new property boundaries or drainage patterns.  Therefore it seems the western part of Brentford went out of use by AD 400, and this area was not occupied again until the Medieval period. The lack of any evidence of Saxon activity or occupation on either site is difficult to explain, though the remains could have been disturbed by Medieval ploughing.

The Brentford Lock excavation 2001: plan showing major Mediaeval features

Mediaeval & Post-Mediaeval
An agricultural use for the Brentford Lock site, from the 12th to 15th centuries, is evident from the presence of field boundary ditches. Three ditches traversed the site from east to west and two ditches were aligned SW-NE; all contained residual Roman pottery and 12th-13th century pottery. Two 14th century gullies ran perpendicular to the High Street, indicating a change in alignment from the earlier ditches, and possibly signifying the beginning of the development of properties along the High Street. The western part of Medieval Brentford became known as New Brentford, and the houses recorded during the excavation would have stood opposite the church of St. Lawrence which was founded in the 12th century.

One of the properties is of interest because of number of hearths at its rear and the length of time in which similar activities were taking place there. Three 15th century pitched tile hearths, possibly used for baking, were discovered, cutting into which was an unusual brick structure with a tiled floor dating to the 16th century. It is not clear what the function of this feature was but it could not have been used as an oven since there was no flue, and because it was buried it would have been difficult to clean out. It seems this property continued to be used as a bakery or kitchen because a large circular brick oven from the 18th century was found directly above these two earlier phases of activity.

By the 19th century the site was densely occupied with houses fronting the High Street, and a substantial tannery located on the River Brent. Many wood-lined tanning pits were found along the river, containing noxious substances which helped to tan the leather. Brick lined soakaways and cess-pits were dug in the back gardens of the houses. Surprisingly one soakaway contained the 19th century figurine of a Roman soldier with a sword, found not far from the Roman roadside ditch.

Studied together, the excavations carried out along Brentford High Street are beginning to reveal the nature and the development of the settlement in the Prehistoric, Roman, Medieval and Post-Medieval periods. The excavation has produced no evidence of a settlement in this part of Brentford during the Prehistoric period, though the activity on the banks of the former Brent in the early Iron Age implies there was settlement nearby.

The chronology and location of the Roman road and its maintenance can be established and the furthest western extent of the Roman settlement has been discovered. It appears that the Roman settlement comprised a mixture of residential and light industrial buildings from the late 1st century through to the late 4th century. The buildings were most likely  to have been timber-framed with clay walls and tiled roofs. The presence of a smithy in the 2nd century upholds the idea that Brentford was a mutatio or relay station, providing fresh horses for official travellers. The archaeological evidence gathered from excavations complements historical documents and provides a resource for understanding the development of Brentford in the past.

Sources Consulted

Canham, R, 2000 Years of Brentford. HMSO 1978

Cotton J, & Parnum, A, Recent work in Brentford: excavations and observations 1974-1982, in London Archaeologist 4 (12), 318-25, 1983

Laws, A,  Excavations at Northumberland Wharf, Brentford, in Transactions of the London and Middlesex Archaeological Society 27, 179-205, 1976

Lorraine Darton was the site supervisor on the Brentford Lock excavations; she worked for Pre-Construct Archaeology Limited in the London region.


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