Generation of focused intensities of 5×1019 W cm-2 by Danson, C, Allott, R, Booth, G, Collier, J, Edwards, C, Flintoff, P, Hawkes, S, Hutchinson, M, Hernandez-Gomez, C, Leach, J, Neely, D, Norreys, P, Notley, M, Pepler, D, Ross, I, Walczak, J, Winstone, T