A Roman would likely have taken issue (and maybe taken offense) with that claim.
The men of Britain are taller than the Celti, and not so yellow-haired, although their bodies are of looser build. The following is an indication of their size: I myself, in Rome, saw mere lads towering as much as half a foot above the tallest people in the city, although they were bandy-legged and presented no fair lines anywhere else in their figure. Their habits are in part like those of the Celti, but in part more simple and barbaric— so much so that, on account of their inexperience, some of them, although well supplied with milk, make no cheese; and they have no experience in gardening or other agricultural pursuits.