Wagstyl, K
Ronan, L
Whitaker, K J
Goodyer, I M
Roberts, N
Crow, T J
Fletcher, P C
Article History
Received: 9 February 2016
Accepted: 19 February 2016
First Online: 12 April 2016
Competing interests
: PCF has received money in the past for <i>ad hoc</i> consultancy services, from GlaxoSmithKline. The remaining authors declare no conflict of interest.