© 2018 Elsevier B.V. I report on a study into how native British English speakers (N = 78) respond to various instances of I'm sorry played to them in an experimental setting. The test items vary in terms of what the speaker is ‘sorry’ for, but are controlled such that the intonation of I'm sorry is kept the same throughout and the recordings are all produced by the same speaker. The results present some challenges for our current thinking about (im)politeness. In particular, examples which we could classify as ‘verbal formula mismatches’ (Culpeper, 2011: 174) such as I'm sorry you are such an arsehole are unexpectedly treated by a significant minority of respondents as being ‘proper’ apologies. I explore how we can account for this type of response and argue that Jucker and Taavitsainen's (2008:6) suggestion that speech acts are ‘fuzzy concepts’ which ‘require a prototype approach’ is a productive one. I outline the parameters along which apologies can be more or less prototypical, including the identifiability of the offence and the speaker's perceived attitude towards it.