From the longer Wikipedia page 
The Battle of Stoke Field (16 June 1487) may be considered the last battle of the Wars of the Roses, since it was the last engagement in which a Lancastrian king faced an army of Yorkist supporters, under the pretender Lambert Simnel. The Battle of Bosworth Field, two years previously, has established Henry on the throne.
Henry VII of England held the throne for the House of Lancaster (House of Tudor), and had tried to gain the acceptance of the Yorkist faction by his marriage to their heiress, Elizabeth of York, but his hold on power was not entirely secure.
An impostor claiming to be Edward, whose name was Lambert Simnel, although it is difficult to say if that was his real name, came to the attention of John de la Pole, Earl of Lincoln. Lincoln, although apparently reconciled with the Tudor king, himself had a claim on the throne; moreover, the last Plantagenet, Richard III of England, had named Lincoln, his nephew, as the royal heir. Although he probably had no doubt about Simnel's true identity, Lincoln saw an opportunity for revenge and reparation.
Lincoln fled the English court on 19 March 1487 and went to the court of Mechelen (Malines) and his aunt, Margaret, Duchess of Burgundy. Margaret provided financial and military support in the form of 2000 German mercenaries, under the commander, Martin Schwartz. Lincoln was joined by a number of rebel English Lords at Mechelen, in particular Richard III's loyal supporter, Lord Lovell, Sir Richard Harleston, the former governor of Jersey and Thomas David, a captain of the English garrison at Calais.
On 15 June, King Henry began moving north east toward Newark after receiving news that Lincoln had crossed the Trent. Around nine in the morning of 16 June, King Henry's forward troops, commanded by the Earl of Oxford, encountered the Yorkist army assembled in a single block, on a brow of a hill surrounded on three sides by the River Trent at the village of East Stoke.
In an unusual military manoeuvre, the Yorkists surrendered the high ground by immediately going on to the attack. The battle was bitterly contested for over three hours, but eventually, the lack of body armour on the Irish troops meant that they were cut down in increasing numbers.
Unable to retreat, the German and Swiss mercenaries fought it out. All of the Yorkist commanders: Lincoln, Fitzgerald, Broughton, and Schwartz, fell fighting. Only Lord Lovell escaped and, according to legend, died hidden in a secret room at his house. Simnel was captured, but was pardoned by Henry in a gesture of clemency which did his reputation no harm. Henry realised that Simnel was merely a puppet for the leading Yorkists. The Irish nobles who had supported Simnel were also pardoned, as Henry believed he needed their support to govern Ireland effectively.
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