1 Royal College of Paediatrics and Child Health, London, UK.
2 Royal College of Paediatrics and Child Health, London, UK; Department of Paediatrics, London North West Hospitals National Health Service Trust, London HA1 3UJ, UK. Electronic address: [email protected].
3 Division of Paediatric Emergency Medicine, Hospital for Sick Children, Toronto, Canada.
4 University of Manchester, Manchester, UK.
5 Royal College of Paediatrics and Child Health, London, UK; Imperial College London, London, UK.