Come on. Hadrian built his little wall to keep out the Picts, who were as gnats compared to the Celts, in terms of the numbers and sheer ferocity of the latter. That is to say, the Picts seem to have disappeared and the Celts, as you well know, ye shall always have with you. BTW, 95% of the Brit histories on this issue [whether or not the Romans concluded that engaging the guys with the blue war paint was a bad career move] are total rubbish. What? You accuse me of bias? My seconds will be contacting you.
well, the picts seem to have become the Highlander folks while the lowlander Scots are descendents of the Scotti tribe that came over from Ireland around the 1st century.