University College London, National and Kapodistrian University of Athens, University College London, University College London - Centre for Rheumatology Research, University College London, University College London, Vascular Noninvasive Diagnostic Centre, Imperial College London, University College London - Centre for Adolescent Rheumatology Versus Arthritis, University College London, University College London and University College London - GOSH and Centre for Rheumatology Research