Lady Margaret Beaufort had been consolidating her position. Upon the death of Henry Stafford, she had married another Yorkist sympathiser, Lord Stanley.
Upon the death of Margaret of Anjou, she had become the leader of the Lancastrians. Her son, Henry Tudor, was their new pretender for the crown. His claim was sufficiently obscure that she had deemed it wise to bide her time rather than assert it in battle. The Beauforts were the illegitimate offspring of the Duke of Lancaster, third son of Edward III. Richard II had legitimated the Beaufort line. Henry IV had added some small print to deny them the right to inherit the throne, but no one reads the small print.
With the death of Edward IV in 1483, the time had come to put her patient planning to the test. The strategy was simple: divide and rule. Edward had willed that Gloucester should act as Protector until his son came of age. She would set Gloucester and the old Yorkists against the upstart Woodvilles, let them destroy each other, then take the spoils.