Using evidence from Aberystwyth English, this study shows two points relevant for the phonetic implementation of the fortis-lenis contrast in plosives and two points concerning the diachronic scenarios proposed as ways in which pre-aspiration (one of the correlates of this contrast) innovates. Firstly, a wide range of acoustic features distinguishes the fortis and the lenis series. Release duration is a correlate of the contrast in three foot-positions (initial: tot vs dot; medial: co tter vs co dder; final: co t vs co d), as is vowel duration and the presence of voicing. Furthermore, pre-aspiration and breathiness differentiate the two series foot-medially and foot-finally. For one speaker, glottalisation rather than pre-aspiration distinguishes the series foot-finally. Secondly, whilst the plosives are frequently post-aspirated foot-initially, the release of /t/ and /d/ is realised variably with affrication and/or post-aspiration in all three positions: rather than presence or absence of affrication or post-aspiration then, it is release duration that distinguishes the series. Thirdly, the data is not supportive of the suggestion that pre-aspiration innovates in the fortis series as a consequence of the loss of voicing in the lenis series or the other way round [1] and [2] or, fourthly, as a step on a degemination trajectory [3], [4].