SNN113233 - A medieval Causeway at 1A london End, Irchester, Northamptonshire: Archaeological Excavation Report

In July and August 2021 an archaeological excavation was carried out by Souterrain in the former rear garden of an early 17th century house at 1A London End, Irchester, Northamptonshire, prior to the construction of a new house. The site lies about 100 m southwest of the former location of a 13th century manor-house and farm. The manorial complex was reportedly excavated prior construction of a housing estate in 1967, although no written, drawn or photographic record is known to have survived. The remains are said to have extended over more than 2 hectares and included the foundations of several buildings. Given the proximity of the present development area it seemed possible that the garden of the 17th century house would occupy a part of the manorial site. In 2020, two small archaeological trial pits were excavated in the garden. One of these, dug in the proposed footprint of a garage, encountered a possible13th century midden deposit that was perhaps associated with the manor. The other, dug close to the proposed house footprint, exposed part of a laid surface of limestone rubble, on which a sherd of late medieval pottery was found. The archaeology was buried under layers of post-medieval horticultural soil. Subsequently, in 2021, an archaeological excavation was carried out in the proposed new building footprint prior to construction groundwork: the subject of this report. The excavation revealed the previously encountered stone surface to be part of a well-built medieval causeway which traversed an ancient tract of marshy ground adjacent to the former course of a brook. The causeway was exposed for a distance of 10 m. Three distinct phases of causeway construction were identified. It appears to have originated in the late 13th century as a raised track-way of cobbles set in clay, at which time it was flanked by a ditch. A more robust causeway of pitched limestone slabs and kerbing was then built over it in the 13th / 14th century. At some juncture in the same period the causeway seems to have suffered severe erosion and subsequently underwent significant repair and widening. It appears to have continued in use into the 14th / 15th century during which time there was a natural accumulation of soil on either side. When a stone-lined drain was built through it in the 16th century it may have been no more than an earthwork. The results of the excavation are compared with those obtained from the 2020 trial pits, particularly with respect to palaeo-environmental data and pottery assemblages. The report explores the historic landscape context of the causeway - its spatial relationship with the manorial complex and its possible route - by means of historic maps and surveys, old aerial photographs and archaeological data. It is hypothesised that the causeway’s construction may well have been a direct response to severe climatic anomalies of the period. Finally, an appraisal of research objectives is provided together with a consideration of the potential for any further study / analysis.