The princes' fate after their disappearance remains unknown, but the most widely accepted theory is that they were murdered on the orders of their uncle, King Richard. Thomas More wrote that they were smothered to death with their pillows, and his account forms the basis of William Shakespeare's play "Richard III", in which Tyrrell murders the princes on Richard's orders. Subsequent re-evaluations of Richard III have questioned his guilt, beginning with William Cornwallis early in the 17th century. In the period before the boys' disappearance, Edward was regularly being visited by a doctor; historian David Baldwin extrapolates that contemporaries may have believed Edward had died of an illness (or as the result of attempts to cure him). In the absence of hard evidence a number of other theories have been put forward, of which the most widely discussed are that they were murdered on the orders of Henry Stafford, 2nd Duke of Buckingham, or by Henry Tudor. However, Pollard points out that these theories are less plausible than the straightforward one that they were murdered by their uncle who in any case controlled access to them and was therefore regarded as responsible for their welfare. An alternative theory is that Perkin Warbeck, a pretender to the throne, was indeed Richard, Duke of York, as he claimed, having escaped to Flanders after his uncle's defeat at Bosworth to be raised with an aunt.