1. Department of Upper Gastrointestinal Surgery, Queen Elizabeth Hospital Birmingham, University Hospitals Birmingham NHS Foundation Trust , Birmingham , UK
2. Institute of Cancer and Genomic Sciences, College of Medical and Dental Sciences, University of Birmingham , Birmingham , UK
3. Department of Surgery, St. Thomas’ Hospital , London , UK
4. Department of Surgery, Portsmouth Hospitals University NHS Trust , Portsmouth , UK
5. Division of Surgery, Imperial College London , London , UK