It's a bit of an "oldest pub" claim and the council has since upgraded it to "Britain's first City" after getting city status in 2022! It's MP called it "the most arrogant council in Britain" which we can add to it's claims for fame.

There were millions of Britons and plenty of other town-worthy settlements with 1000s of years of human activity but they were mostly proto-literate. There had been 100s of years of trade with Greeks/Romans but pre-conquest writing is imperious enough to refer to land masses or at best the Oppidum (town/stronghold/capital) of a Celtic king but not deign to record the local name.

The key for Colchester was being where someone who could write cared enough to do so. The Roman invasions started in the South East and the Catuvellauni led the resistance. Once defeated the Romans set up a fortress on the site of their capital Camulodunum later turning it into the official colonial capital. Now that it's Roman, it becomes acceptable enough for Pliny to write down it's name.

My best effort to spite Colchester City Council is with coin inscriptions. Celtish Kings with sufficient Roman influence e.g. Gaulish tribes that had migrated, would mint coins with latin script and here is one with that refers to the capital where it was minted 100s of years before Pliny:

https://www.britishmuseum.org/collection/object/C_1988-0627-...

https://en.wikipedia.org/wiki/Calleva_Atrebatum

It's the capital of the Atrebates, Calleva Atrebatum. The oppidum of a king minting coins is a good enough to be a "town" for an HN comment. Congratulations to Silchester in Hampshire!

And a candidate for the location of Camelot, thanks to its Roman name, Camulodunum.