Many scholars have held that in late Middle English, in the London dialects from which Standard English grew there existed a vowel /y:/ developed from various native sources and/or used as a substitute for Old French or Anglo-Norman /y/. The aim of this article is to accurately review the relevant evidence adduced by E. J. Dobson and other scholars in favour of a variation between early Modern English /y:/ and /iu/ with a view to offering conclusions based on a direct presentation of the original sources. It will be shown that even the early writers on orthography and pronunciation who correctly describe a sound [y] (as they knew it from French, Scottish and Northern English, as well as from other languages) cannot be adduced as evidence for the existence of a vowel /y:/ in early Modern English.