Section of the Grandpont causeway

Reasons for Designation

Although a basic network of roads was already in existence as part of the Roman road system, new towns and communication needs led to the construction of an extensive network of new roads throughout England during the medieval period. This network, much of which has now been disturbed or obscured by the modern road system, included causeways, fords and bridges. The Grandpont represents an example of a causeway, few of which now survive in their original form. Although this example has been obscured by later alterations and additions, original fabric is visible from the river whilst partial excavation has demonstrated the survival of substantial archaeological remains beneath the modern road surface. The causeway is thought to have its origins in the Saxon or early Norman period and represents an important element in understanding the layout of early medieval and medieval Oxford. It is one of the very few examples where both detailed archaeological and documentary records are available.

Details

The monument includes a 500m-long section of the Grandpont causeway which crosses the Thames floodplain to the south of Oxford. The causeway is buried beneath the modern line of the Abingdon Road and is encased in later widening and revetting. However, exposed sections of the Norman stonework, forming several of the arches and piers which make up the causeway, can be seen from the river beneath. The earliest phase of the ragstone causeway was between 3.9m and 4m wide and was constructed as a continuous linear structure with arches set along its length where river channels or drainage needs dictated. Within the section of the causeway south of Folly Bridge and north of White House Road there are eleven arches, six of which are visible, while the rest have been filled in over the years. The causeway has been widened on at least two occasions, giving it a modern width of c.12.5m. It is likely that evidence survives for earlier Saxon or Norman wooden bridges beneath the Grandpont, while it is known from excavation at 33 St Aldates that a Saxon ford, which preceded the causeway, went out of use and silted up to the extent that by the late 12th century it was covered with 1.25m of accumulated silt. It is believed that the Grandpont is part of the `Great Bridge' built by Robert d'Oilly who also built Oxford Castle. The Folly Bridge, located midway along this section of the Grandpont, also known as `Friar Bacon's Bridge', is a later medieval feature and included a six-sided tower with portcullis, drawbridge and heavy gates which provided a barrier to any enemy approaching the South Gate of the city along the causeway. This was partially demolished and rebuilt in 1826 having become `so decayed' by the time of Waterloo (1815) that it was no longer safe. The tower foundations survive in the river bed. The bridge is listed Grade II. In addition to the remains visible from the river, evidence for the survival of the Grandpont has been provided by a number of excavations and observations using existing manholes and during essential works on service trenches. These have provided evidence that the structure survives along this 500m section and beyond, although the majority of observations and the visible remains are contained in this stretch. Although the original core only measures c.4m wide, the preservation of the monument depends upon the entire width of the carriageway (c.12.5m) being included in the scheduling. Excluded from the scheduling are the 19th-century reconstructed elements of the listed Folly Bridge, the modern road carriageway and its make-up as well as the drainage culvert and all existing service trenches which run along the causeway, although the ground beneath all these features and beneath and around the service trenches is included in the scheduling.

MAP EXTRACT The site of the monument is shown on the attached map extract.

Legacy

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

Legacy System number:

21757

Legacy System:

RSM

Sources

Books and journals
Durham, B, Newsletter in Oxford: Abingdon Road and Folly Bridge, Vol. 11, (1981), 129
Durham, B, Oxoniensia in The Thames Crossing at Oxford: Archaeological Studies 1979-82, Vol. XLIX, (1985), 57-

Other
Title: Plan of Folly Bridge and Granpont Source Date: 1590 Author: Publisher: Surveyor: Plan in Brasenose College Archives
Discussion of O.A.U. work on sites, JEFFERY, P.P., Discussion between B. Durham and P. Jeffery, (1992)
Colour prints taken from punt, SCHOFIELD, J., Field visit photographs from SM file, (1992)
PRN 6358, CAO, Folly Bridge, (1987)

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