Professor Leech is Emeritus Professor of  English Linguistics at Lancaster University. He has written, co-edited and co-authored over 25 books and over 100 articles in the areas of linguistics and English language, especially in stylistics, English grammar, semantics, pragmatics and corpus linguistics.

He was co-author, with Randolph Quirk, Sidney Greenbaum and Jan Svartvik, of the monumental and authoritative A Comprehensive Grammar of the English Language  (Longman 1985). In pragmatics, too, his Principles of Pragmatics (Longman 1983) has been a landmark text. He is a Fellow of the British Academy, and a Member of Academia Europaea.