Archaeologists from the Museum of London have discovered the foundations of London’s earliest found medieval tide-powered mill.
The discovery was made at Greenwich Wharf during archaeological investigations in conjunction with Erith Contractors Ltd to prepare for the building of a new residential development by London and Regional Properties.
Experts from the museum say the structure, which measures ten metres by twelve metres at its base, would have had a wheel diameter of over 5 metres and has been dated to the twelfth century.
Tidal mills worked by drawing in water from the river as the tide rose and releasing it as it fell, powering the mill. The Greenwich wheel features a “substantial” intact fragment of the waterwheel and an enormous trough to channel the water which was shaped out of a single oak beam.
The museum describes the mill as “an unprecedented and rare find” and says it appears to have been constructed in two phases from prepared oak beams, on which carpenters’ construction marks are still clearly visible.
Damian Goodburn, Museum of London’s ancient timber specialist identified the beams as being cut with an axe rather than a saw, initially suggesting an early medieval date. Dendrochronological analysis (where tree rings are counted) has supported this observation dating the trees’ felling to 1194. A large curved section of the waterwheel itself was found preserved within the water trough allowing archaeologists to estimate the diameter of the wheel at around 5.2 metres – an incredible size for a wooden structure of this type and testament to the craftsmanship and engineering skills of its makers.
Simon Davis, Contract Manager for Museum of London Archaeology, said: “Tide mills may have been numerous along the Thames foreshore in the early medieval period. Four mills in Greenwich are mentioned in the Domesday book of 1086 and over 6000 mills were recorded across the country at this time. However, little evidence of mills in use in the early medieval period has been found on archaeological sites, so the discovery of a 12th century tide mill at Greenwich is very significant and exciting. Detailed recording of the find following its excavation and dismantling by the Museum of London Archaeology field team will enhance our understanding of milling technologies and early medieval economies.”
Following consultation with English Heritage, who continue to monitor the site, the structure has been dismantled, with each timber carefully recorded. Key sections of the find, including the trough and the waterwheel, have been removed and are currently undergoing conservation by the conservation department at York Archaeological Trust.
Mark Stevenson of English Heritage said, “The discovery of the remains of this wooden tidal mill at Greenwich Wharf, Greenwich, is likely to be the earliest medieval example of this type to be excavated in London. English Heritage is working closely with Greenwich Borough Council, the developers and Museum of London Archaeology to ensure that this rare and important discovery is carefully recorded.”