During her time as queen, Catherine Howard had engaged in a number of extramarital affairs. Most notably, she had been involved in a long-term relationship with Thomas Culpeper, a courtier and close friend of the king. Culpeper was executed for his role in the affair on 10 December 1541, and Catherine was subsequently arrested.
Upon her arrest, Catherine was initially very cooperative. She confessed to her adulterous relationship with Culpeper and acknowledged that she had other lovers before her marriage to the king. However, she denied that she had committed high treason.
Catherine's trial began on 28 November 1541. She was found guilty of high treason and sentenced to death on 10 December. Her execution took place on 13 February 1542, at Tower Green.
Catherine's execution was a major scandal that rocked the English court. It led to a number of reforms designed to prevent future queens from engaging in similar behaviour.