No longitudinal studies have reported rates of pre-aspiration across the lifespan of an individual, and few have investigated changes in local breathiness and glottalisation vis-à-vis pre-aspiration, though they have been previously shown to feed and block the phenomenon. We examine the speech of Queen Elizabeth II, finding decreasing rates of pre-aspiration over the course of her life alongside decreasing local breathiness and increasing glottalisation. This finding of pre-aspiration in 20th-century Received Pronunciation suggests that its presence in modern Standard Southern British English, first noted recently among young speakers, is not a sudden innovation.
Kettig et al. (Sun,) studied this question.