These pictures, circulated for the pleasure of colleagues a few years ago, came to the notice of some pupils. One of them noted the antiquity of the stones and asked whether the Romans had made the weir.
No. It was built in the 11th century by the Earl of Chester, so that the Abbey of St Werburgh could have a watermill. Of the hundreds of weirs all over the country, it is not easy to establish which ones were put there in Roman times, and many are perhaps of greater antiquity.
Weirs go back to prehistory, in this and other countries, notably Canada. Their early use was to trap fish; but both Greeks and Romans devised the first watermills: and for a watermill to function efficiently and continuously, a weir is needed, to create what engineers call a head of water. The weir at Chester is at the highest tidal point of the Dee, although at a very high spring tide, sea water flows over it.
The Romans may not have built a weir, but they made Deva into a flourishing port, which it continued to be until the early 19th century, and they stationed the Twentieth Legion there. It was in fact a major fortress, and its importance in the North West can be gauged from its change of name: it began to be called just Castra—The Camp; and the Welsh name likewise is Caer.
A visit to the Grosvenor Museum gives a vivid idea of life in this Roman community, which has been continually inhabited since, and its central streets and much of the wall are still in the same positions.
The legionaries stationed at Chester seem to have kept a high profile. For the removal of doubt about their presence, they stamped their logo everywhere on tiles, artefacts and buildings, and even stencilled it as a graffito on walls:
LEGIO VICESIMA VALERIA VICTRIX