“Inevitably, both counsel referred me to the frequently-cited observations of Leggatt J in Gestmin SGPS SA v Credit Suisse (UK) Ltd[2013] EWHC 3560 (Comm) about the fallibility of human memory and the weight to be placed upon documentary evidence, leading to the conclusion (at [22]) that “the best approach for a judge to adopt in the trial of a commercial case is, in my view, to place little if any reliance at all on witnesses' recollections of what was said in meetings and conversations, and to base factual findings on inferences drawn from the documentary evidence and known or probable facts”