Moreover, it appears that the fact of the princes having been murdered was held in great doubt for a long time afterward. Even More himself, writing about thirty years later, is obliged to acknowledge that the thing had "so far come in question that some remained long in doubt whether they were in Richard's days destroyed or no." This is certainly remarkable, when it is considered that it was of the utmost importance for Henry VII to terminate all controversy upon the question. Yet Sir Thomas tells us that these doubts arose not only from the uncertainty men were in whether Perkin Warbeck was the true duke of York, "but for that also that all things were so covertly demeaned, one thing pretended and another meant, that there was nothing so plain and openly proved but that yet, for the common custom of close and covert dealing, men had it ever inwardly suspect." All this, it is urged, may very well suggest that the doubts were reasonable, and that the princes in reality were not destroyed in the days of Richard III. And, indeed, when we consider how many persons, according to More's account, took part in the murder or had some knowledge of it, it does appear not a little strange that there should have been any difficulty in establishing it on the clearest evidence. For besides Tyrell, Dighton, and Forest, the chief actors, there were Brackenbury, Green the page, one Black Will, or Will Slaughter, who guarded the princes, and the priest who buried them, all fully aware of the circumstances of the crime.