Le Sueur spent some time in London, 1788–92, then returned to Paris where the revolution was going on. Three of his operas were performed, and he became professor at the École de la Garde Nationale, and then at the Conservatoire which was very new at the time. There he taught basic music theory. He was unable to get any more operas of his performed. He wrote a book saying how music should be taught in France, and criticizing the Conservatoire and its director. Because of that he lost his job at the Conservatoire.