In an article on the fortress defences, I discussed the likely survival of Chester's Roman defences into the early medieval period. Clearly some of the Roman fortress wall was still standing at the time, since parts of it are still standing now, but it may not have been fully intact.
During Roman government, Chester was a legionary fortress situated in the territory of the Cornovii, whose tribal capital was at Wroxeter (Viroconium Cornoviorum). Could it have become an important ecclesiastical centre in the early medieval period?
601 The synod of Urbs Legionis [Chester].
Some of the dates in Annales Cambriae are two or three years different from those of the same events given by Bede (see article on Dating the Battle of Chester), so this is likely to be the synod referred to by Bede at which Archbishop Augustine of Canterbury met a group of Brittonic bishops at a date in 603 or 604 (Ecclesiastical History, Book II Ch. 2). Bede doesn't specify the location of the meeting, but says that it was attended by seven bishops and many very learned men mainly from Bangor-is-Coed. Bangor-is-Coed is about 18 miles from Chester, so this would be consistent with the synod being held in Chester.
A lead salt-pan discovered at Shavington, near Nantwich, bore the inscription Viventi [Epis]copi (White & Barker 2002; Keith Matthews website). The first word translates as "of Viventius", and the second could mean either that Viventius was the episcopus or that Viventius was subordinate to the episcopus. Episcopus was used of a bishop (whence the modern term "episcopal"). However, it could also mean "overseer" or "supervisor". So the inscription could refer to a bishop who owned a salt works, or to the foreman of a salt factory. It is impossible to rule out either, although as Viventius is the name of a Christian saint, I'm inclined to agree with Keith Matthews that the bishop is a more likely interpretation than a factory overseer.
The Synod at Chester must have been an important event, at least in the opinion of whoever thought it worth recording in Annales Cambriae. So it is a reasonable interpretation that Chester in 601/603 was a centre considered suitable for such an event. This may reflect surviving infrastructure capable of handling a large number of VIPs - seven bishops and their retinues, plus "many learned men", probably amounted to quite a lot of people. The possibility of surviving Roman infrastructure at Chester in the early medieval period, in addition to the fortress defences, is discussed in another article. It may also indicate that Chester was a prestigious site, the sort of place where one would choose to invite a foreign dignitary (Augustine). If it was also under the control of a wealthy churchman, that would fit very well.
Salt was a vital commodity, needed for preserving food over the winter, and so salt production can be expected to have continued in some form long after the end of Roman administration. If the bishopric of Chester controlled the income from a salt works, that could have provided a substantial source of revenue in addition to whatever income was gained from the local agricultural population. An additional source of revenue would have helped to maintain Chester as a prestigious site (since it had the resources to maintain, repair or replace buildings), and could have contributed to the bishop's ability to put on a big event like the Synod.
Cities run by bishops existed in fifth-century Gaul, where Sidonius Apollinaris, bishop of what is now Clermont-Ferrand in the Auvergne, governed his city and negotiated with the local king (of the Goths) in 470-480. The other city known from the civitas of the Cornovii, Wroxeter, had a complex of impressive timber houses in Roman style built on the site of the baths basilica in the late sixth century, and it has been suggested that the frigidarium of the baths was used as a church (as happened in Leicester) and that the rebuilding was organised by a bishop who controlled the city (White & Barker 2002). Perhaps Chester was also run by a bishop in the early medieval period - and perhaps his name was Viventius
Annales Cambriae, available online.
Bede. Ecclesiastical History of the English People. Translated by Leo Sherley-Price, Penguin Classics, 1968, ISBN 0-14-044565-X
Mason DJP. Roman Chester: city of the eagles. Tempus, 2001, ISBN 978- 0-7524-1922-0.
White R, Barker P. Wroxeter: Life and death of a Roman city. Tempus, 2002, ISBN 978-0-7524-1409-7.