He had been bound by an honourable promise not to open any such letters if they did arrive, but to repair to the National Gallery, where his colleague would meet him at ten o'clock.
He didn't open the letters but brought them with him to meet his colleague.
mnli hypothesis: He didn't open the letters but brought them with him to meet his colleague. premise: He had been bound by an honourable promise not to open any such letters if they did arrive, but to repair to the National Gallery, where his colleague would meet him at ten o'clock.