Keith Moffatt FRS is Emeritus Professor of Mathematical Physics at the University of Cambridge. He has served as Head of the Department of Applied Mathematics and Theoretical Physics, and as Director of the Isaac Newton Institute for Mathematical Sciences in Cambridge. A former editor of the Journal of Fluid Mechanics, he has published papers in fluid dynamics and magnetohydrodynamics, and was a pioneer in the development of topological fluid dynamics. He is a Fellow of the Royal Society, a member of Academia Europæa, and a Foreign Member of the Academies of France, Italy, the Netherlands and USA. He has been awarded numerous prizes, most recently the 2018 Fluid Dynamics Prize of the American Physical Society. Emmanuel Dormy is a Centre National de la Recherche Scientifique (CNRS) Directeur de Recherche at the Department of Mathematics and its Applications at the Ecole Normale Supérieure (ENS) in Paris. He is also a professor at the ENS and at the Ecole Polytechnique, where he teaches different aspects of fluid dynamics. Convinced of the need to embrace all aspects of the dynamo problem, in 2006 he started a research group at the ENS which promotes an interdisciplinary approach and jointly studies all geophysical and astrophysical aspects of dynamo theory. He also founded and directed the Dynamo-GDRE, which promotes exchanges among researchers working on all aspects of dynamo theory throughout Europe and beyond, and he organises widely attended annual meetings.