In Great Britain as in the US, two cultural sub-nations identify themselves (and the other) as North and South. The US’s North and South are quite clearly delineated, by the states’ affiliations during the Civil War (which in the east coincides with the Mason-Dixon line). That line has become so emblematic that the US South is referred to as ‘Dixieland’.
There’s no similarly precise border in Great Britain, maybe because the ‘Two Englands’ never fought a civil war against each other.There is, however, a place used as shorthand for describing the divide, with the rougher, poorer North and wealthier, middle-to-upper-class South referring to each other as ‘on the other side of the Watford Gap’.
Not to be confused with the sizeable town of Watford in Hertfordshire, Watford Gap is a small village in Northamptonshire. It was named for the eponymous hill pass that has facilitated travel east-west and north-south since at least Roman times (cf. Watling Street, now passing through it as the A5 motorway). Other routes passing through the Gap are the West Coast Main Line railway, the Grand Union Canal and the M1, the UK’s main North-South motorway.