“Stay safe!” — A wish, advice, or an order?

Abstract This paper offers a diachronic analysis focussing on the different uses and forms that the expression stay safe acquired throughout the Covid-19 pandemic. It makes an original contribution to the study of historical pragmatics by drawing on data traditionally examined in the field of linguistic landscape studies and produced during a global health crisis, resulting in an innovative, real-time study of pragmatic change in progress. Drawing on a corpus of 3,032 public signs photographed in London between March 2020 and December 2021, the paper shows how the expression stay safe was used as a wish and a parting formula in the early stages of the pandemic, and then reverted to a directive function on signs implementing containment measures, illustrating a trend opposed to that typically found in historical pragmatics. It also discusses the variability characterising the data, and the ambiguity of the expressions that are analysed, typical of ongoing pragmatic change.