What influence did the Celtic languages, present in the British isles, have on the formation of English? As far as I can see, there seems to be no clear example of a major Celtic influence, other than a few loan words. Rather, there's many suspected instances of Celtic influence (c.f. the Northern subject rule), although even these seem to be hotly disputed.
Why is the Celtic influence so small, seeing as some places in England were still speaking Celtic languages until very late, and two of England's bordering nations have native Celtic languages which survive to this day?