The scene where Elizabeth asks the Spanish ambassador to marry her to Dudley at a firework party did take place, but the assassination attempt that followed is fictional. (Although it is true that many attempts were made on her life.)

The film rolls two conspiracies against Elizabeth into one. The first was the Ridolfi plot of 1571, in which the Duke of Norfolk was executed and Arundel arrested. The second culminated in 1586 when a priest named John Ballard was sent by the Pope to coordinate an English Catholic rebellion that would clear the way for an Italian invasion. As far as we know, Sussex and Dudley were not involved in any treachery as alleged in the film. Importantly, the film makes scarce mention of Elizabeth's cousin Mary, Queen of Scots (as a Catholic it was she who the rebels wished on the English throne and she played a central role in all the conspiracies).