Several of the world’s languages exhibit double determination structures, including English dialects which have a construction with a demonstrative determiner and a locative adverb (e.g. this here book). Doubling in demonstratives has commonly been explained as a language’s response to a loss of deixis, leading to a linguistic cycle. However, this explanation cannot be sustained for English because demonstratives are fully functioning grammatical deictics (e.g. this book). In this article, we probe the role of doubling in the history and grammatical development of English double demonstratives with evidence from rural UK dialects. Using quantitative methods and the principle of accountability we calculate proportion of forms and patterning in simple and double demonstratives, enabling us to demonstrate that the doubled form has particular discourse-pragmatic functions, most notably, to flag topics in discourse. Our findings lead us to make two theoretical proposals. First, double demonstratives in English are used for discourse-pragmatic purposes; and second, doubling led to a new, complex determiner suitable to take over discourse-pragmatic functions from simple determiners (complexification of the determiner paradigm). Finally, we suggest that obsolescing features like the English double demonstrative offer key insights for understanding the development of linguistic systems.