Scotland and a Greater England?

Arthur Herman, How the Scots Invented the Modern World: The True Story of How Western Europe's Poorest Nation Created Our World and Everything in It (New York: Three Rivers Press, 2001), 20:

• England and Scotland had been joined together by history and geography since the fall of the Roman Empire.... Both spoke the same language, since the Scottish royal court had adopted English (or a dialect related to Middle English called Scots) back in the eleventh century, relegating Gaelic to the cultural backwater.

We did not, I believe, incorporate this point into our Early Modern England, 1485-1714.