As the UK government makes a mess of its lockdown easing, again politicians, journalists and commentators on social media deploy Offa's Dyke as short-hand for the divide between England and Wales. While often said in jest, this reveals deep-seated misunderstandings and stereotypes about Offa's Dyke and its role in the contemporary landscape, but more importantly it sheds light on how entrenched ethnonationalisms influence the perception of early medieval monuments.