which can easily be "translated" into:
Charles le roi, notre grand empereur
sept ans tous pleins a été en Espagne
[?] la mer conquis la terre [?]
Il n'y a aucun chateau qui devant lui reste [I think I can see how the verb "to remain" crawled into English]
Granted, quite a few of the words were more recognizable since I'm also familiar with Portuguese, Spanish, and Catalan, yet the first four lines of "Sir Gawain and the Green Knight" (late 1300s), written over two centuries after the Song of Roland, is, at first sight, barely understandable to modern English speakers, and can only be "translated" after a closer look and more easily if one is at least remotely familiar with the development of English orthography:
[?] the siege and the assault was ceased at Troy,
The [?] [?] and [?] to [?] and asked,
The talk that the [?] of [?] there wrought
Was tried for his treachery, the truest on Earth
In short, why does it seem that English underwent a more radical change than French?