Henry's court was a place of constant positioning for the king's favor. Henry's hangers-on were always vying for power, and Henry Howard, Earl of Surrey, lost his life when the Seymours felt threatened.
Jane Seymour was Henry's third wife. She died soon after they married, but delivering Henry a legitimate male heir helped maintain the Seymours' power. But the Howards, too, had the king's ear. Henry Howard's father had been entrusted with the upbringing of Henrys VIII's illegitimate son by Elizabeth Blount. One sign of favor at court was an allegiance by royal marriage, and there was talk of two possible suitors for Henry's young daughter, princess Mary. One was a Seymour, Jane's brother; the other was Henry Howard. This set the stage for a battle.
The Seymours told the king that Howard had quietly supported the Catholics in a rebellion against the Supremacy Act in 1536. Howard had actually fought against the rebels, but the accusation still landed him in prison for two years. After he got out, he started making trouble for the Seymours, trying to block a marriage between his sister and one of the Seymours and making various accusations questioning the Seymours' loyalty to the king.
The Seymours struck their final blow: They again accused Howard of supporting the Catholics, but this time, they made his sister testify against him. She admitted on the stand that her brother was, in fact, a devoted Catholic. This was seen as a rejection of the king's supremacy. The Seymours combined this testimony with the fact that Henry Howard's father had had a claim to the throne before Henry VIII became king (though he never fought for it), and they convinced the king, who was by that time very ill, that the Howards intended to usurp the throne.
Henry Howard, Earl of Surrey, was beheaded in 1547, the same year the king died. It was Henry VIII's last execution. Howard had written volumes of poetry while imprisoned, and ended up creating the form that eventually came to be called the Shakespearean sonnet [source: Britannica].
The Howards and the Seymours were powerful, but they were nothing compared to Thomas Cromwell, the king's chief advisor during the successful break from the Catholic Church. Cromwell had the king's ear for eight years -- a long time in the world of Henry VIII. He lost his head only after he succeeded where all others had failed.