By February 1487 Lambert Simnel had appeared in Ireland, claiming to be Edward, earl of Warwick, the young son of Edward IV's brother George, duke of Clarence.... Earl Lincoln sailed from the Netherlands to Dublin, with some 2000 mercenaries supplied by Margaret. Whether out of fond memory of the Irish administration of Richard, duke of York, resentment at Henry's restoration of the Butler earls of Ormond, or sheer opportunism, most of the Irish political community had recognized Simnel as king. At Dublin on 24 May, led by Gerald Fitzgerald, earl of Kildare, the lord deputy recently confirmed in office by Henry, they crowned him as Edward VI. Backed by several thousand Irish troops in addition to Margaret's mercenaries, Simnel and his patrons landed at Foulney Island on the Cumbrian coast on 4 June and marched across northern Lancashire, over the Pennines and rapidly southwards, gathering support from Ricardian die-hards. Henry moved through Leicester to Nottingham, steadily assembling a large army - probably twice the size of his rivals' - from the retinues of loyal peers and household knights. At East Stoke, near Newark, on 16 June, Henry's archers decimated the unarmoured Irish levies, and after hard fighting his vanguard, again under Oxford, put the rebels to flight. Complete though his victory was, Henry spent the next four months moving cautiously through the midlands and north, venturing as far as Newcastle to secure the region's loyalty.

Henry VII... was an extremely clever man, possibly the cleverest man who ever sat on the English throne.... The mask he wore was to some extent deliberately inhuman. He wished to be remote and incalculable; he wished to be more feared than loved. He could not afford to be generous without seeming to be weak. Yet Henry was generous to Lambert Simnel and, at first, to Perkin Warbeck, although ruthless and relentless enough in his treatment of Suffolk (the son of Edward IV's sister) who was kept in prison for years after being hunted all over Europe, and of Warwick (son of the Yorkist Duke of Clarence) who was executed after fourteen years in the Tower.

Henry VII... was not a vindictive man, and his style of government was quiet and efficient, never using more cruelty or deceit than was necessary. When he captured Lambert Simnel, the young tradesman's son who led the first revolt against him and was crowned King of England in Dublin, he did not put him to death, but employed him as a servant in his household. When he defeated and captured a second and far more dangerous pretender, Perkin Warbeck, he spared his life, and it was only after Warbeck had twice tried to escape that he was executed.

Of the revolts faced by Henry VII, the most serious were those with dynastic intentions. The imposture of Lambert Simnel as the imprisoned nephew of Edward IV, Edward, earl of Warwick, however exotic, was much more menacing, because it occured within two years of Bosworth. Perkin Warbeck's imposture as Edward IV's younger son, Richard of York, during the 1490s was more easily contained, despite Scottish and European intervention. Simnel was routed at the battle of Stoke: his promoters were slain or imprisoned, and the young imposter was taken into the royal household as a servant.