Henry VIII married Catherine of Aragon as his father's dying wish, and through this was happily married to her for 18 years, until he started to worry increasingly about getting a male heir to his throne as he had only one child, a daughter, Mary. Henry then mad eup a story about Catherine of Aragon and that she in fact had consummated her marriage with Edward therefore making their marriage wrong in the eyes of god and therefore they must divorce. The pope didn't agree.
The pope's refusal to annul the marriage was contributory to the Reformation of English churches and the eventual establishment of the Church of England, a break from the Roman Catholic church.