It is hard to think of a more committed public intellectual in Britain in the twentieth century than Lionel Robbins—except, of course, John Maynard Keynes. For six decades Robbins engaged in public debate on economic policy issues in lectures and talks, contributions to newspapers and magazines, and articles and books. He had the opportunity to influence UK economic policy directly during the Second World War. After the war he exerted a strong influence on government policy toward the arts and higher education. The irony is that he is also known for his apparent claim in his best-known book, An Essay on the Nature and Significance of Economic Science, that academic economists should not indulge in such activity. The present essay describes how he fulfilled what he saw as his duty to use his expertise to enlighten nonexperts, especially once he became professor of economics at the London School of Economics in 1929.