In 1487, Elizabeth of York is crowned Queen of England in a ceremony also attended by her beloved husband, Manuel the Fortunate who became the future King Manuel I of Portugal after his nephew Alonso died in an accident.
Though the Yorkist victory at Bosworth secured the throne in their hands, the death of Richard at the same battle placed a great emphasis on the cousins of the White Rose to secure a viable and lasting dynasty. This fell upon the shoulders of Elizabeth of York, daughter to Edward IV and beloved niece of Richard III. Though linked to Henry Tudor, his death at the hands of Lord Stanley, his own step-father, had ended the hopes for the Lancastrians to see their house on the throne again.
Suitors had been rejected - in 1469, she was briefly betrothed to George Neville, son of John Neville, Earl of Northumberland, who initially supported Edward IV against the rebellion of his own brother Richard Neville, 16th Earl of Warwick, but later joined Warwick's rebellion, so the betrothal was called off. In 1475, Louis XI agreed to let her marry his son, Charles, the Dauphin of France, but Louis reneged on the promise in 1482. Instead, Elizabeth was linked with the related monarchs of Portugal. By contrast to the powerful suitors of France or Holy Roman Empire, the young Manuel had grown up in similar circumstances to his new bride. Both had seen cousins kill each other in conspiracies and murder as well as on the battlefield.
Their union led to lasting peace and sealed the alliance of John of Gaunt and King John of Avis and would lead to the reign of King Henry VII of England and I of Portugal (28 June 1491 - 28 January 1547) and the "Golden Age" of the Anglo-Portuguese Empire.
(Addendum by Jeff Provine)
With its newly found political stability, the shared Anglo-Portuguese court was the perfect place for an exasperated Italian navigator, Cristoforo Colombo, to head after being repeatedly turned down for financing in his ideas for an expedition sailing west to create a new trade route to India. Young King Henry was advised that the eventual route around Africa after the successful 1488 voyage of Bartholomeu Dias around the Cape of Good Hope, but Henry felt that if there were to be another route, he would want it. He dispatched Columbus, who returned successfully after claiming an island he dubbed "Henryland."
Columbus believed it was India, but it was soon discovered that the territory was a New World. As Columbus became intolerable, Henry had him executed and sent more explorers to swarm over the coasts his growing empire, such as the later Sir Francis Drake's conquest of the Inca. A few French and Dutch colonies interrupted the sprawling Anglo-Portuguese Empire, but it became the foundation for international trade in language and economics.
Overwhelmingly religious Spain continued its march into Africa and seemingly perpetual war against the Moors. Meanwhile, religion would end up tearing the Anglo-Portuguese apart as the north turned more Protestant, and the empire's golden age would come to an end. A new empire from Germany would arise centuries later, eclipsing the French and creating a new world order.
From the good folks over at Today in Alternate History