The nunnery of Sion and the manor of Isleworth were given by Edward VI. to the Protector Somerset, who at once pulled down the conventual buildings, using the materials for the foundation of the present mansion, that was still uncompleted when its owner's career was cut short by his attainder for high treason. The property then reverted to the Crown, and in 1553 it was given by the young king to John Dudley, Duke of Northumberland, who had been mainly responsible for the downfall of the Protector. The {282} duke seems to have finished the work of his predecessor, for soon after he took possession of Sion House his son, Lord Robert Dudley, brought home to it his bride, the ill-fated Lady Jane Grey; and it was there that the crown was offered to her on the death of Edward VI. Thence the nine days' queen started by river in a state barge, attended only by a few adherents, on her fatal journey to the Tower, whence four months later she was led forth to execution, after having looked down from her window on the mangled remains of her husband as they were being carried away to their last resting-place. After the death on the scaffold of the Duke of Northumberland Sion House once more reverted to the Crown, and Queen Mary gave it back to the Brigittines, but few of them cared to return to their transformed old home; and two years later even those few were driven forth again by Queen Elizabeth, who lent the house first to one and then another of her favourites. In 1604 the estate was granted by James I. to Henry Percy, Earl of Northumberland, who nearly lost it through his complicity in the Gunpowder Plot, for which he suffered many years' imprisonment and had to pay a fine of £11,000. He returned to Sion House only a short time before his death, bequeathing it to his son, Algernon Percy, who was made guardian of the children of Charles I., the Dukes of York and Gloucester and the little Princess Elizabeth, who died the year of her father's execution. The royal prisoners, for such they were, appear to have been very happy in their Isleworth retreat, for they were {283} often allowed to go and see their father at Hampton Court, and it was not until they were taken to London to bid him farewell, just before his death, that they realised how terrible was their own position.