Andrew Liddle is Professor of Astrophysics at the University of Sussex. He was previously at Imperial College. He is an authority on the theoretical side of astrophysics and cosmology, in particular on the origin and evolution of the structure of the universe. Jon Loveday is Senior Lecturer in Astronomy at the University of Sussex. He has previously held positions at the University of Chicago, Fermi National Accelerator Laboratory, and the Australian National University.