He is an academic, far from being mainstream/famous elsewhere. But you have a point, in his field, social education, he may be a very known figure (academically speaking, extremely far from being “famous”). He is only famous in Br due to his involvement with politics, otherwise he would just be considered an academic as well. IE: His best selling book, "Pedagogy of the Oppressed", has sold less than 1MM copies (all versions). Paulo Coelho has sold more than 100MM copies of his "The Alchemist" novel (worldwide).