The UK is under fire for pulling up the drawbridge for bright foreign students by limiting visas and complicating the application process. This column argues that welcoming large numbers of foreign PhD students bodes well for countries and universities interested in scientific and engineering innovation. Science and engineering are, after all, critical for the growth and competitiveness of industrial economies. Policies that serve to limit or discourage the enrolment of international graduate students lead to reductions in the rate of scientific discovery.