Henry VIII didn't have any trouble letting people know what he was thinking. Unfortunately, he was constantly changing his mind. When it came to his succession, it took him three times to get it right.
His First Act of Succession was passed by Parliament on this day in 1534.
The Succession Portrait by Hans Holbein shows Henry seated with his heir Edward and Edward's mother Jane Seymour (painted posthumously). Mary is shown standing on the left side of the portrait, and Elizabeth on the right.
Prior to Henry's marriage to Anne Boleyn, Henry's only living legitimate offspring, Mary, was the presumptive heir. England had never had a female monarch before, which was a possible dilemma for the country, but a major personal dilemma for Henry. He wanted to make sure the Tudor line was secure on the throne of England, and he felt the best way to do that was with a son.
When Henry divorced Mary's mother, Catherine of Aragon (who herself had descended from a ruling, female monarch), he pushed through an Act of Succession that named Mary illegitimate, and his children with Anne as his heirs to the throne. Unfortunately, Anne also gave birth to a daughter, and she fell out of favor with the king before she could give him any more children. After Anne's execution, Henry pushed through a Second Act of Succession, that removed both Mary and Elizabeth from his official line.
Unfortunately, this left England once again without an heir. So on he went.
Henry's third wife, Jane Seymour, was the charm. She gave birth to a son, giving Henry his longed for male heir. As a male, Henry's son Edward was the heir presumptive.
Near his death, Henry was reconciled with his daughters. This was largely due to the influence of Katherine Parr, Henry's sixth and final wife. His Third Act of Succession, which he also pushed through Parliament, returned both dauthers to the line of succession. In order, Edward, Mary and Elizabeth were all named as heirs. Each of them would rule England. None of them produced offspring and the Tudor line died out with Elizabeth. So much for all of Henry's careful planning.
Henry's foresight to have the document ratified by Parliament is what secured Mary's and Elizabeth's claim to the throne. Without it, England's golden Elizabethan Age would never have happened.