“...for one party to seek orders striking out passages in witness statements served by the other. Often enough, objections are raised but left to be resolved at trial. To do otherwise may be disproportionate, and inconsistent with the overriding objective. A judge is able to identify that which is admissible evidence and that which is not. But it is not unknown, or even exceptional, for objections to be raised and resolved before trial. There can be good reasons for doing so.”