The authors are grateful to the patients who agreed to take part in these studies. The following clinicians recruited patients to the studies: Dr. W. Tucker—Alexandra Hospital; Prof. D.T. Sharpe—Bradford Royal Infirmary; Mr. I. Foo—BUPA Hospital Elland; Dr. H. Galvin—Calderdale Royal Hospital; Dr. P.C. Lorrigan—Christie Hospital; Dr. M. Middleton—Churchill Hospital; Dr. N. Cox—Cumberland Infirmary; Dr. G. Ford, Dr. G. Taylor—Dewsbury and District Hospital; Mr. A.R. Groves, Mr. R. Matthews—George Eliot Hospital; Dr. A. Layton—Harrogate District Hospital; Dr. M.J. Cheesbrough—Huddersfield Royal Infirmary; Dr. A. Carmichael, Mr. H. Siddiqui, Mr. M. Coady—James Cook University Hospital; Dr. M. Goodfield, Dr. R. Sheehan-Dare, Dr. S.M. Wilkinson, Mr. Browning—Leeds General Infirmary; Dr. J.M. Eremin, Dr. T. Watts—Lincoln County Hospital; Dr. Brunt—Mid Staffordshire General; Mr. P. Baguley—Middlesborough General Hospital; Dr. M. Brunt, Mr. J. Roberts, Mr. P. Davison—North Staffordshire City General; Dr. D. Fyfe—Nottingham City Hospital; Mr. L. Le Roux Fourie, Mr. O.M. Fenton—Pinderfields General Hospital; Dr. S. McDonald-Hull—Pontefract General Infirmary; Dr. Maraveyas—Princess Royal Hospital and Castle Hill Hospital; Dr. N. Steven, Dr. Peake—Queen Elizabeth; Mr. T.E.E. Goodacre—Radcliffe Infirmary; Dr. M.L. Wood—Rotherham District General Hospital; Mr. A. Batchelor, Dr. P. Patel, Mr. H. Peach, Mr. M. Liggington, Mr. S.L. Knight, Mr. S. Kay—St James's University Hospital; Dr. J.A.A. Langtry—Sunderland Royal Hospital; Mr. Sugden—University Hospital Hartlepool; Mr. R.B. Berry, Mr. S. Rao—University Hospital North Durham; Dr. Stewart—Walsall Manor Hospital; Dr. Ilchyshyn—Walsgrave; Mr. P.W. Griffiths; Dr. M. Marples—Weston Park Hospital; Dr. E. Marshall—Whiston Hospital; Dr. Lewis—Worcester Royal Infirmary; Mr. D. Murray—Wordsley Hospital and Selly Oak Hospital; Dr. A.S. Highet—York District Hospital and Scarborough Hospital.