[1] Hull Royal Infirm, Kingston Upon Hull, N Humberside, England
[2] Royal Free Hosp, London, England
[3] UCL, London, England
[4] Royal Victoria Hosp, Cardiac & Thorac Surg, Belfast, Antrim, North Ireland
[5] Chelsea & Westminster Hosp, Genitourinary Med, London, England
[6] UCL, Div Surg & Intervent Sci, London, England