These pictures, circulated for the pleasure of colleagues a few years ago, came to the notice of some pupils also. 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, but many are of great antiquity.
The making of weirs goes back to prehistory, as is clear in this and other countries, notably Canada. Necessity created their first use—to trap fish: but both Greeks and Romans soon devised the first watermills: and for a watermill to function efficiently and continuously, a weir is necessary, its function being to create what engineers call a head of water. The weir at Chester also marks the highest tidal point of the river, although at a very high spring tide, sea water may flow over it.
The Romans may not have built the weir, but they made Chester 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 name: the inhabitants called it just Castra—The Camp; and the Welsh name likewise is simply Caer.
A visit to the Grosvenor Museum gives with vividness an idea of life in this Roman community, which has been continually inhabited since, with its central streets and much of the wall still in exactly the same positions.
The legionaries stationed there 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 apparently even stencilled it as a graffito on walls:
LEGIO VICESIMA VALERIA VICTRIX