1. Upper Gastrointestinal and Bariatric Unit, Heartlands Hospital, Heart of England NHS Foundation Trust; Birmingham UK
2. Health Informatics; University Hospital Birmingham NHS Foundation Trust; Birmingham UK
3. Quality and Outcomes Research Unit; University Hospital Birmingham NHS Foundation Trust; Birmingham UK
4. Directorate of General Surgery, City Hospitals Sunderland NHS Foundation Trust; Sunderland UK
5. Department of Upper Gastrointestinal and Bariatric Surgery; Musgrove Park Hospital; Taunton UK