In 1553 his father attempted to put Robert’s sister-in-law Lady Jane Grey on the throne of England; the plot failed, and Northumberland and his sons were arrested and imprisoned in the Tower of London. Northumberland and his son Guilford, husband of Jane, were executed, but Robert was released in 1554. During his stay in the Tower he may have met Princess Elizabeth, imprisoned there by her sister Mary.
Amy Robsart died in childbirth during Robert’s imprisonment. Robert Dudley was therefore free to marry Elizabeth, and they had two sons. However Elizabeth refused to allow Dudley to be crowned king and, after an ill-conceived plot to seize power, Dudley was arrested and convicted of treason. He was imprisoned in the Tower of London, in the same tower where he had been held as a boy; Elizabeth refused to sign the warrant for his execution, and he died there.