The turmoil within was quickened by encouragement from without.

The Yorkist sympathies of the Earl of Kildare, the deputy of Ireland, offered a starting-point for a descent from the west; while the sister of Edward the Fourth, the Duchess Margaret of Burgundy, a fanatic in the cause of her house, was ready to aid any Yorkist attempt from Flanders.

A trivial rising in 1486 proved to be the prelude of a vast conspiracy in the following year.

The Earl of Warwick, the son of the Duke of Clarence and thus next male heir of the Yorkist line, had been secured by Henry as by Richard in the Tower; but in the opening of 1487 Lambert Simnel, a boy carefully trained for the purpose of this imposture, landed under his name in Ireland.

The whole island espoused Simnel's cause, the Lord Deputy supported him, and he was soon joined by the Earl of Lincoln, John de la Pole, the son of a sister of Edward the Fourth by the Duke of Suffolk, and who on the death of Richard's son had been recognized by that sovereign as his heir.