LAMBERT SIMNEL, English impostor, was probably the son of a tradesman at Oxford. He was about ten years old in 1487, and was described as a handsome youth of intelligence and good manners. In 1486, the year following the accession of King Henry VII, rumours were disseminated by the adherents of the Yorkist dynasty that the two sons of Edward IV, who had been murdered in the Tower of London, were still alive. A young Oxford priest, Richard Symonds by name, conceived the project of putting forward the boy Simnel to impersonate one of these princes as a claimant for the crown, with the idea of thereby procuring for himself the archbishopric of Canterbury. He set about instructing the youth in the arts and graces appropriate to his pretended birth; but meanwhile a report having gained currency that the young Earl of Warwick, son of Edward IV's brother George, Duke of Clarence, had died in the Tower, Symonds decided that the impersonation of this latter prince would be a more easily credible deception.

It is probable that Symonds acted throughout with the connivance of the Yorkist leaders, and especially of John de la Pole, Earl of Lincoln, himself a nephew of Edward IV, who had been named heir to the crown by Richard III. The Yorkists had many adherents in Ireland, and thither Lambert Simnel was taken by Symonds early in 1487; and, gaining the support of the earl of Kildare, the archbishop of Dublin, the lord chancellor and a powerful following, who were, or pretended to be, convinced that the boy was the Earl of Warwick escaped from the Tower, Simnel was crowned as King Edward VI in the cathedral in Dublin on the 24th of May 1487. Messages asking for help were sent to Margaret, Duchess of Burgundy, sister of Edward IV, to Sir Thomas Broughton and other Yorkist leaders.

On the 2nd of February 1487 Henry VII held a council at Sheen [Richmond Palace] to concert measures for dealing with the conspiracy. Elizabeth Woodville, widow of Edward IV, was imprisoned in the convent of Bermondsey; and the real Earl of Warwick was taken from the Tower and shown in public in the streets of London. But although Lincoln is said to have conversed with Warwick on this occasion, he fled abroad immediately after the council at Sheen, where he was present. In Flanders, Lincoln joined Lord Lovell, who had headed an unsuccessful Yorkist rising in 1486, and in May 1487 the two lords proceeded to Dublin, where they landed a few days before the coronation of Lambert Simnel. They were accompanied by 2000 German soldiers under Martin Schwartz, procured by Margaret of Burgundy to support the enterprise, Margaret having recognized Simnel as her nephew. This force, together with some ill-armed Irish levies commanded by Sir Thomas Fitzgerald, landed in Lancashire on the 4th of June.

King Henry was at Coventry when the news of the landing reached him, and immediately marched to Nottingham, where his army was strengthened by the addition of 6000 men. The invaders met with little encouragement from the populace, who were not well disposed towards a monarch whom it was sought to impose upon them by the aid of Irish and German mercenaries. Making for the fortress of Newark, Lincoln and Sir Thomas Broughton, at the head of their motley forces, and accompanied by Simnel, attacked the royal army near the village of Stoke-on-Trent on the 16th of June 1487 [cf. Battle of Stoke. After a fierce and stubborn struggle in which the Germans behaved with great valour, the Royalists were completely victorious, though they left 2000 men on the field; Lincoln, Schwartz and Fitzgerald with 4000 of their followers were killed, and Lovell and Broughton disappeared never to be heard of again. The priest, Symonds, and Simnel were taken prisoners. The former was consigned to a dungeon for the rest of his life; but Henry VII, recognizing that the youthful pretender had been a tool in the hands of others and was in himself harmless, pardoned Lambert Simnel and took him into his own service in the menial capacity of scullion. He was later promoted to be royal falconer and is said to have afterwards become a servant in the household of Sir Thomas Lovell. The date of Simnel's death is unknown, but he is known to have been still living in the year 1534.