Crystal, like Hawking, is British. Also like Hawking, and more to the point, he has popularized an academic discipline. That is not say he has not done significant if arcane (which is normal) work within the academic discipline itself--he has. But helping us understand better how the world works--whether in regard to physics or language or God's sovereignty--is I would venture more significant and probably even harder than arcane research.
Crystal has made many of the facets of language clear to us when we thought we understood how it worked but in reality were lost in the dark. Two of his more successful popular books are The Stories of English and Txtng: The Gr8 Db8.