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South Mimms Castle

Also known as, or recorded in historical documents as;
South Mymms; castle on the Lea; Super Lviam

In the civil parish of Potters Bar.
In the historic county of London and Middlesex.
Modern Authority of Hertfordshire.
1974 county of Hertfordshire.
Medieval County of Middlesex.

OS Map Grid Reference: TL22970260
Latitude 51.70831° Longitude -0.22185°

South Mimms Castle has been described as a certain Timber Castle.

There are earthwork remains.

This site is a scheduled monument protected by law.


Castle comprising a 9m high motte in the NW corner of a kidney-shaped bailey 390' x 350'. There are traces of an outer bailey to the S, now ploughed. There has been extensive lime-quarrying to the W of the monument; the quarry is now infilled and planted.
Excavations revealed that the construction and finds were consistent with the assumption that the castle was built by Geoffrey de Mandeville in 1141 with a charter from Matilda, and was possibly destroyed in 1143. It is also possible that earlier manorial buildings were demolished when the castle was built. The 'motte' is unusual, but not unique, in its construction and purpose. The timber tower was built first, and earth built up around its base to ensure stability, with access into the tower through a timber-lined tunnel. The visual result was not one of a raised mound within the bailey (Davidson).
Finds of 13C/14C material in the vicinity suggest some form of later occupation on the site. (Hertfordshire HER)

It has been incorrectly suggested that a Royal licence to crenellate was granted in 1141 July (Click on the date for details of this supposed licence.).


It may well be that the motte at South Mymms is unusual purely in being fully excavated but that in practice this form of work, a timber revetted mound of earth supporting a tower or house, was a more normal form. In a field trip with the Castle Studies Group in 2010 Davidson reports that he knew of 23 mottes which had excavated sufficiently for the form to known and of these 20 were the timber revetted type (although sometime in layers of revetments. See also the Bayeux tapestry portrayal of the motte at Bayeux)
Charters granted to Manderville in 1141 mention his 'castle on the Lea' in terms that some have taken to be a licence to crenellate. Coulson, in his paper on Anarchy castles, footnotes ' The 'castle on the Lea' could be Hertford, or one of two possible sites near Bow Bridge, or in Luton. His association with South Mimms is purely conjectural' (See records for Hertford Castle, Hertfordshire; Luton Holly Lodge, Bedfordshire; Bow, Middlesex). However, if it were Hertford there seem no reason it would not be called Hertford and much the same could be said about a castle in Luton. The site at Bow is dubious as a castle site. South Mimms is clearly a castle of the right date and in roughly the right place, although not somewhere of such significance as to be clearly known by name. It is not, however on the River Lea which is a few miles to the east, although it is on a small tributary. The conjecture that this is Geoffrey's castle is entirely reasonable but not certain.
The village of South Mimms has moved location since the C12 and the castle was not isolated when first founded. The original parish church may well have been at the castle site although this was an area of dispersed settlement and the village may not have actual nucleated until after the castle was built.
Links to archaeological and architectural databases, mapping and other online resources

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Sources of information, references and further reading
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This record last updated 26/07/2017 09:21:01

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