The Silures where a tribe of Celts who according to Roman historians defeated The Second Legion. There's some doubt as to whether the Silures were ever subdued by Roman Forces or whether an agreement was reached. The Silures, apparently were not to be changed as a people by either "clemency or cruelty." They were "born curly haired" and were darker complexion than most Celts of the Islands of Britannia who apparently were a redder variety of Celt and many suggested the Silures were more like the Celts of Gaul and Iberia. The suggestion being that, as a people, they had moved from somewhere like Northern Spain to the South East of Wales, the River Usk and even Gloucestershire, and, the argument goes, they'd have done this by a sea crossing from the Iberian Peninsular to the Severn Estuary rather than nipping across the Straits of Dover. Mind you, Romans were tricky and often very subjective historians.
For the Victorian investigators, most of whom were gentlemen of leisure, class
and race were established categories, the big thing was broadening the mind by
reaffirming the overall superiority of the Anglo Saxon. Most considered the
earlier inhabitants of the English Islands rather primitive, relative to say
Romans or Greeks, so the Celtic Myths took a distant place to someone like
Tacitus. One such Victorian investigator's interest in rocks took him to the
borders of Wales and England, where he observed layers of rocks, some of which
contained fossils and he devised a system for giving rough dates to rock strata
which he named The Silurian System, after the curly haired Silures. The Silurian
geologic period begins at the end of a major extinction of species, about 60% of
all water species were wiped out, and during the Silurian age jawed and bony
fish took on a whole new look and vascular plants took a hold on the idea of
living on land.