Producers are getting jittery again. Large-scale shows look risky when a single infection can postpone an entire show. Hence Poirot and More in the West End. This is a conversation piece in which David Suchet talks about his career as Agatha Christie’s most celebrated nosy parker. Not much technical rehearsal is needed and Suchet relies on the support of a single performer, Geoffrey Wansell, who feeds him easy-peasy questions.