Approximately 1,500m of this considerable earthwork is located within Erddig Park (SJ 3260 4851 ? 3225 4685). The site consists of a bank up to 2m high with a ditch on the west side. The dyke probably represents a boundary between the Anglo-Saxon kingdom of Mercia and the Kingdom of Powys in the 8th century. Wat's Dyke consists of several discontinuous lengths of bank in an area centred on Wrexham. The better known Offa's Dyke was subsequently built further to the west and although the dykes never actually merge the later dyke appears to reflect the prior exisitence of Wat's Dyke. It is though to have been built by the Mercian king Aethelbald (AD716 - 57) who was succeeded by his cousin Offa (AD758 - 96) following assassination by his retinue. These dykes or banks were not intended to be a serious obstacle to movement like Hadrian's wall but served as a control and a major boundary marker. Neither form a complete barrier - there are areas where no bank was ever built ie where forest (long gone) formed a satisfactory boundary. This is especially the case in South Wales. Also at least one instance where a stream (the Morda Brook) had been canalised to form the frontier . Various pipelines for water and gas have been cut through the dyke over the years. Although not on Trust land an access road was cut through the dyke in 1990 and Clwyd-Powys Archaeological Trust undertook an assessment at the time. The resultant report concluded that the profile was indeed one of bank with ditch on the western (Welsh) side.

John Latham RCAHMW 11 June 2013