Conservation organisations are tasked with protection of biodiversity but are challenged by limited resources; consequently, the highest conservation priority species have designations that should correspond with the level of protection needed. In Britain, the saxicolous Calicium corynellum receives the highest conservation priority as a consequence of its rarity, combined with dramatic population declines over the last several decades, having disappeared from 2 of its 4 British sites and declined in one other. However, there is some uncertainty associated with the taxonomic status of the entity referred to as C. corynellum in Britain, partly because its common congener, C. viride has been recorded on trees overhanging several of the populations of C. corynellum, but also because the morphology of British material is very similar to the common C. viride, but found on rock. Standard fungal barcode nr ITS sequences of C. corynellum from both extant British populations of C. corynellum were successfully amplified, along with C. viride from trees overhanging one of the sites and from other British sites. In addition, morphological features were compared among specimens of both taxa. There is no evidence to support the distinction of British C. corynellum from its more common congener, and its conservation status is Britain should be re-evaluated.