Linda Colley wrote a book called "Britons: Forging the Nation, 1707-1837" that examines how British identity was formed after the Act of Union (the act that united Wales and Scotland with England). Her answer to the question of how British identity was formed out of these disparate local identities is that several wars with France caused "British-ness" to become the identity of choice.

Even before this time period, England and France had a tumultuous relationship (the Hundred Years War, England's Protestantism vs. France's Catholicism, the on-again, off-again relationship that France had with Scotland). Thus, when constructing English (and more broadly British) identity, writers, politicians, educators, etc. tended to overlook England's Anglo-Norman phase in favor of its Germanic roots.