Purpose: The purpose of this paper is to explore the period of uncertainty created by the referendum. The focus is the UK real effective exchange rate (REER). The authors set out to measure the additional impact of the uncertainty surrounding the referendum. The authors distinguish this from the longer trend value of Sterling. Design/methodology/approach: The study applies a reduced form exchange rate model, first introduced by Edwards (1994), and makes use of Bank of England daily data for the period November 2015–July 2016. Findings: The results indicate a sharp depreciation of Sterling with reference to its long-term trend. The authors set out some of the possible context which may account for fluctuations during the referendum campaigning period. This can be distinguished from other longer-term factors likely to be previously responsible for trend depreciation, and also from the further sharp depreciation effects triggered by the referendum outcome. The principal finding is that during the week of the referendum, up to the declaration of the result, exchange rate depreciation deviated from the long-run trend by approximately 3.5 per cent, but the actual immediate effect on the exchange rate was an 8 per cent depreciation. Over the period from the announcement of the referendum, the exchange rate fluctuated markedly around its trend and one can also identify a larger effect based on the “wrong-footing” of markets at the point when the outcome was announced. Research limitations/implications: The research has important implications, as one might further infer that this marks a step change in attitudes to Sterling as Brexit became a real issue rather than a notional concern. One can thus consider the exchange rate as both symptom of and indicator for determinations of the underlying economic strength or weakness of the economy. In essence, it has acted as a litmus test. Practical implications: The research has important practical implications in understanding the dynamics of the exchange rate market and the role of uncertainty in its dynamics. Social implications: The study has important social implications as the changes to exchange rates are a perennial cause for concern. Exchange rates sit as one among many problems for the contemporary UK economy. Brexit has resulted in a significant subsequent depreciation of Sterling. Inter alia, though the immediate effect of Brexit on growth was muted due to unexpected sustained consumer spending, throughout the latter half of 2016 and the first two quarters of 2017, business investment slowed, the rate of deficit reduction slowed (but without any concomitant meaningfully rise in government investment in infrastructure, etc.) and both main measures of inflation began to rise. Originality/value: The study contributes to the existing body of knowledge by exploring the period of uncertainty created by the referendum and its implications for the UK REER. The study differentiates and reflects on the weakness of Sterling due to the weak external position of UK’s economy and the further role played by the uncertainty surrounding Brexit. In this sense, it important contribution to theory as well as practice.