Spreading everwhere?

There is no doubt that glottalisation of syllable-final stops in Received Pronunciation is on the increase, but this has sometimes been taken to imply that the feature has mushroomed as a late 20th-century phenomenon. This paper sets out to show that glottalisation is actually of some antiquity. Explicit references (by reputable linguists) to glottalisation in the standard language date from the early 1920s, while audio recordings going back even further provide us with direct proof. If apparent time is taken into account, such data could indicate that glottalisation was quite common from at least the mid-19th century onwards.