Funding for this research was provided by:
Economic and Social Research Council (ES/N000404/1)
Medical Research Council (MR/L01999X/1)
Received: 5 September 2018
Accepted: 11 January 2019
First Online: 13 February 2019
Ethics approval and consent to participate
: Ethical approval was granted by the National Research Ethics Service London-Westminster, the St Thomas’ Hospital Research Ethics Committee (EC04/015 and 07/H0802/84). All research participants have signed informed consent prior to taking part in any research activities.
: All authors have read and approved the manuscript for publication.
: The authors declare that they have no competing interests.
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