One of the largest Kingdoms was that of the Brigantii or Brigantes tribe, who controlled much of northern Britain, including Lancashire and Cumbria. The Brigantes seem to have accepted being client kings under Roman rule ( selling out some of the tribes nearby in the process), to retain a fairly independent continuation in an area of the West coast that Rome wasn’t much interested in anyway.
Records are scarce, but those in the know say the Setantii tribe of the Brigantes controlled what is now Lancashire all the way down to the Mersey, though in all likelihood as not much more than overlords to the people in settlements away from the major population centres. There has long been debate over the term for their major sea port, deconstructed as the ‘port of the Setantii’.
‘Portus Setantiorum’ ( or Segantiorum Portus) was referred to by the Roman historian Ptolemy, with some academics over time even claiming this was Liverpool, assuming that the reference itself ( in Geographica of Claudius Ptolemaeus) is correctly listing places in geographical order around the coast. While nothing is totally impossible in this world, that theory can be filed neatly under the highly improbable label, with Carlisle, Lancaster, Fleetwood or Warrington all having far greater odds of being the port referred to. Not least because they actually existed at the time. Which helps.
For my money, though I have nothing to base it on beyond similarity of names Caernarfon ( the Roman ‘Segontium’) has just as good a shout, but I digress.
We know very little about the Setantii, though some have associated them with Ireland and the Irish mythical figure Cuchulain ( aka Setanta). We don’t even know for sure that their power extended to the Mersey ( the equally land hungry Cornovii tribe controlled just over the water in the Wirral so who’s to say they didn’t stake a claim to the North of the Mersey too). What is likely is that life didn’t change much for the people living here, except for one thing…