I’ve been asked about the pronunciation of /s/ in initial strings of /str/.
I know that it is common to pronounce it with a post-alveolar, apical articulation in Glasgow and London (David Abercrombie was talking about its occurrence in Glasgow at least forty years ago, and I have heard it from many Londoners myself). I’m now being asked how prevalent it is in English as a whole, and as none of my pronouncing dictionaries mention it (why should they?), and John Wells’ Accents of English doesn’t either (unless I’m just not seeing it), I’m hoping that someone can throw more light on it. It’s not a variant I use myself, but that might also be a feature of my age.
Presumably, those who have the apical allophone use it also in their pronunciation of words such as syringe, when said in a single syllable: /srɪndʒ/.