Makes and models of devices included in study.
All 90-minute face-to-face assessments took place in central London between October 2015 and January 2016 and were conducted by one of seven researchers who were trained and tested in all relevant protocols. All participants gave informed, written consent. The analytical dataset was pseudo anonymised with each participant given a study number so that individuals could not be identified. Ethical approval for data collection was given by University College London (UCL) (Ethics Project Number: 6338/001) and, for analysis, by the University of Southampton (Ethics Project Number: 18498). Participants received feedback on their results, advice to contact their General Practitioner if their blood pressure was elevated, and a gift voucher.During the assessment, each participant was assessed in the sequence shown in 