The first thing to remember is that The Tragedie of Cymbeline is, despite its published title, a comedy. It’s certainly not a Shakespearean ‘history’ so we mustn’t expect any degree of accuracy or verisimilitude. If anything it belongs to a genre we’d nowadays happily accept as Fantasy if it was to be written up in modern language. And its sources, particularly Geoffrey of Monmouth’s so-called History of the Kings of Britain, were pure fantasy, in the broadest sense, albeit with some authentic pieces like nuts or fruit included in the baking of a cake.
The map I’ve used is a Renaissance edition of Roman geographer Ptolemy’s great work, mapping the world as known at the time. Everything appears distorted but at least north is to the top instead of to the left as in most medieval maps. I’ve marked in Milford Haven in Pembrokeshire near where most of the later action takes place. I’ve made the assumption that Cymbeline’s palace is in Lud’s-town or London, on the walls of which Cloten promises to raise Posthumus’ severed head on a pole (and where medieval traitor’s heads were similarly displayed). Sadly for Cloten he doesn’t get to keep his promise. The historical Cunobelinus, the original Cymbeline (Cynfelyn in Welsh) actually had his ‘capital’ at Colchester in Essex, then called Camulodunum; incidentally, the latter site, named after the god Camulos, may have inspired the choice of ‘Camelot’ as Arthur’s capital.
The Roman fleet came from Gallia, but probably Shakespeare imagines it coming from a Breton port up the western seaways. The overland route taken by Imogen and Cloten west over the river Severn and the Welsh mountains to Milford is marked in green, mostly following the Roman roads that Ptolemy’s map marks out. This rather ‘squeezed’ depiction of Britain allows relatively quick movement from east to west since the chronology of Cymbeline is also particularly squeezed. Modern road or rail routes cut journey times but all Imogen, say, could manage was a score of miles a day on horseback, and to get from London to Milford at this rate would have required a fortnight’s travel (if indeed London was Cymbeline’s capital).
However, in the confines of Shakespeare’s great ‘wooden O’ such considerations were irrelevant. And 450 years ago today — or thereabouts — such considerations were inconceivable to the newborn William about to cry his lungs out.