ABSTRACT To what extent can we detect echoes of the triumphant Britannia (Thomas Arne composed Rule Britannia in 1740) in contemporary Brexit debates? What were the subliminal refractions of the refrain ‘Britons never will be slaves’ in complaints about the frequently evoked ‘Brussels shackles’? Through a longue durée approach to two major elements of modern British history – Britannia and the celebration of colonial expansion as a ‘bringer of progress’, this article charts the persistence of political and cultural visions including the Empire simultaneously as an expression, a tool and a channel of British exceptionalism. Positing that the Empire was integral to the emergence of British identity and its consolidation, it also underlines, through references to John Robert Seeley’s highly influential work, the key role played by England in this process. Based upon the hypothesis that past reflections on Britain’s global role – including those championed by Cecil John Rhodes – have left an imprint on the Brexit conversation in the run-up to, and aftermath of, the vote, this article introduces the concept of ‘imperial factor’ as a way of taking into account the long-term impact that the development and possession of the world’s largest empire has left on British ways of seeing the world, and, crucially, of seeing Britain’s place in the world. Beyond the case-study of exceptionalism offered here, further research, especially of a quantitative nature, is suggested to refine our understanding of the precise extent to which the ‘imperial factor’ played a role in the Brexit vote of 2016. Conceived as an instrument to take into account the potential imperial dimension of a multi-faceted phenomenon such as Britain’s departure from the EU, the ‘imperial factor’ is, more broadly, a useful tool to gauge – in the UK but also among other formerly imperial nations – the potential and variable long-term influence that the possession of an empire left on national visions, psyche and practices.