Short answers, pulled from the story.
John Dudley, 1st Duke of Northumberland (1504-1553) was an English military officer and politician who served as Vice-Admiral and Lord High Admiral under Henry VIII and became the de facto regent of England during the reign of the young King Edward VI from 1550 until 1553. He was the son of Edmund Dudley, a minister of Henry VII who was executed by Henry VIII.
Northumberland's son Guildford Dudley married Lady Jane Grey on the 21st of May 1553, and after Edward VI altered his succession document to name Jane as heir, Northumberland signed the engagement to perform the King's will alongside twenty-three others. Whether the scheme was Northumberland's plot or genuinely Edward's own initiative remains disputed among historians; at his execution Dudley said he had been "procured and induced" by others.
Dudley led a coup of privy councillors in October 1549 that forced the Duke of Somerset, England's Lord Protector, out of office after Somerset's agrarian policies and autocratic style alienated his colleagues. By the 2nd of February 1550 Dudley had become Lord President of the Council, serving as de facto regent for the twelve-year-old Edward VI.
As Lord High Admiral from 1543, Dudley created the Council for Marine Causes, the first body to co-ordinate all naval maintenance tasks, making English naval administration the most efficient in Europe. He introduced formation manoeuvring and co-ordinated gunfire by squadrons ordered by size and firepower, and directed fleet operations at the Battle of the Solent in 1545. He also championed English voyages of exploration to Morocco, the Guinea coast, and a planned Northeast Passage expedition under Hugh Willoughby.
Northumberland was convicted of high treason on the 18th of August 1553 for his role in placing Lady Jane Grey on the throne after Edward VI's death, an act that directly challenged Mary Tudor's claim as queen. He was executed on the 22nd of August 1553 at the Tower of London before a crowd of ten thousand people.
Since the 1970s, historians have moved away from the Victorian "wicked Duke" interpretation. Dale Hoak concluded in 1980 that Northumberland was "one of the most remarkably able governors of any European state during the sixteenth century." Scholars now credit him with revitalising the Privy Council, stabilising England's finances, ending costly wars with France and Scotland, and pursuing religious reform in line with Edward VI's own convictions.