He was also absolutely scathing about "children" who didn't take the opportunity the school offered to learn Latin because he considered that unless they learned it they had effectively dismissed any chance of understanding about 40% of the English language.

This is true from the point of view of vocabulary (as I think the remark was intended), but also very true in terms of learning grammatical structure. In my experience, learning Latin, and the terms applied to the grammatical constructions, helped tremendously in cementing my understanding of such things in English (as well as the Romance languages). Having to understand notions like contrary to fact conditionals, and the hortatory subjunctive, in order to really get where the Latin text was going, kept those concepts in my head more clearly than English class ever did - since I could speak English without learning all that gobbledygook.