1 Department of Paediatrics, University of Oxford, Children's Hospital, John Radcliffe Hospital, Oxford OX3 9DU, UK. Electronic address: fiona.moultrie@trinity.ox.ac.uk.
2 Oxford Uehiro Centre for Practical Ethics, Faculty of Philosophy, University of Oxford, Oxford, UK.
3 Department of Paediatrics, University of Oxford, Children's Hospital, John Radcliffe Hospital, Oxford OX3 9DU, UK.
4 Institute of Metabolism and Systems Research, University of Birmingham, Birmingham, UK.
5 Nuffield Department of Anaesthetics, John Radcliffe Hospital, Oxford, UK.