Learn Latin from Old English :)
Puttering around the web, I found a Grammar by an Anglo-Saxon monk to teach old english speakers/readers Latin
So another challenge beyond Magister Croft and Carolus and Maria.
Ælfric was a wonderful writer of many, many texts, mostly with a religious theme.
Unfortunately, some of his works were responsible for twisting the understanding of the "Christian message" with total fiction, mainly because of short passages of his being distorted by other writers and storytellers. Much of this distortion of his works persisted through the Middle Ages in England and elsewhere, and is often still indirectly responsible for many misunderstandings today.
Nearly 1000 of his greatest works were destroyed or badly damaged in a fire at the Cottonian Library in London in 1731, and around ten years afterwards those that survived were transferred to the British Museum that had just been established by a new Act of Parliament.
This is very cool, thanks! Proj. Gutenberg proofreading is usually quite thorough. This book must have been a real bear to do!
It looks like from the preface (Praefatio) that this is a translation into Old English of excerpts from Priscian's Latin grammar, Institutiones, which was (I've read) the Latin grammar in the middle ages. I'd never heard of Ælfric, FWIW, but he's obviously a big name among Old English writers, acc. to Wikipedia--and I should have, as halfway through one of the books linked to below there's another copy of his Latin grammar.
Somebody on Duolingo posted about learning Anglo Saxon (i. e., Old English), several months back. Here are a few links collected then. If you are a fan of Old English, maybe you would like to do a sort of "reverse course" to your link, Old English via Latin? Here's a grammar of Old English in Latin, and an Old English-Latin dictionary, with as a bonus Ælfric's grammar (which is where the link should open; it is the first part of the book that contains the dictionary).
Also suggested back then was a YouTube video in Latin about learning Old English. It's not a grammar but rather written to urge that one learn Old English, as well as French and Latin, in order to really have a command of modern English, its main purpose being to recommend a YouTube channel, Leornende Eald Englisc, for learning Old English. There is an English version of the video too, I see now.
Or maybe ChrisV351540 would be interested. It would be great to learn Old English, but it's about half a dozen languages from the top of my list, which means I'll never have time to learn it, unless maybe I live to be a hundred.
Anyway, thanks again for the link to Ælfric's Grammar.
Bits of Latin I can recognize! and not natural language acquistion as it starts by naming the parts of speech:
Partes orationis svnt octo eahta dǣlas synd lêdensprǣce:
nomen, pronomen, verbvm, adverbivm, participivm, conivnctio, praepositio, interiectio. nomen is nama, mid ðâm wê nemnað ealle ðing ǣgðer gê synderlîce gê gemǣnelîce
quis hoc fecit? hwâ dyde ðis? ego hoc feci ic dyde ðis:
tu ðû; ille sê.
ego lego ic rǣde, tu legis þû rǣtst, ille legit hê rǣt.