This plot aimed to assassinate the Protestant Queen Elizabeth I and replace her with Catholic Mary, Queen of Scots.
Norfolk confessed to corresponding with Mary's supporters and was taken to the Tower of London. He was executed on 2nd June 1572 after being found guilty of high treason.
Click here to read more about the life of Thomas Howard, 4th Duke of Norfolk.
Also on this day in Tudor history...
Image: My photo of the National Portrait Gallery portrait of Thomas Howard, 4th Duke of Norfolk.