Andrew Wiles was born and educated in England but emigrated to the United States and is still, I believe, a professor at Princeton University. In 1993 he presented a proof of the "Taniyama-Shimura" conjecture. It asserted that every one of a certain type of elliptic function could be associated in a specific way with a modular form. Not at all an elementary subject and not obviously connected with Fermat's Last Theorem. However, Gerhard Frey had earlier proved that Fermat's Last Theorem was true if and only if the Taniyama-Shimura conjecture was true!
Clearly, it was a group effort and a remarkable achievement.
Probably the most accessible discussion is still Simon Singh's book "Fermat's Enigma".
Until you can get that book (check your local library), here is a website with links to several sites talking about Fermat's Last Theorem: