Edward VI was only 15 when he died in July, 1553. The Duke of Northumberland seized upon Edward's death to put his daughter-in-law, Lady Jane Grey, upon the throne, but this attempt came to nothing. Lady Jane was put in prison, and Mary, eldest daughter of Henry VIII, was crowned queen on 10 July, 1553.
Mary was a devout Catholic, and one of the tasks she saw as essential to the spiritual well being of the realm was for her to foster the Catholic faith. One of the ways she could do that was to marry a devout Catholic and produce Catholic heirs. After prolonged negotiations a marriage was arranged between Mary and Philip, son of the Spanish Emperor Charles V.
When the Spanish marriage was announced, Sir Thomas Wyatt the younger (born about 1521 - died 1554) took action. Wyatt was a courageous leader and a skilled soldier, but he was also reckless and hotheaded. He had served for a short time as sheriff of Kent, were he had his estate of Allington Castle. Wyatt considered the marriage an affront to English sovereignty - both spiritual and material. He saw it as the thin edge of a Catholic wedge which would undo the reforms of Henry VIII and draw England under the influence of the Catholic church and the very Catholic Spanish empire.
Wyatt evolved a daring and dangerous plot to raise armies in different parts of the country and converge upon London. The most prominent of his fellow conspirators were Henry Grey, Duke of Suffolk, Sir Peter Carew, and Edward Courtenay, Earl of Devon. To Grey fell the task of raising troops in Leicestershire, while Courtenay did the same in Devon. More troops were expected from the Welsh borderland.
Like many such plots during the turbulent Tudor period, Wyatt's plans were uncovered. Courtenay turned against him, and the other conspirators did not, or could not, fulfil their part in the plan. But Wyatt, perhaps foolishly, went ahead with his rebellion; he raised an army of some 3000 men in Kent, and marched on London. Wyatt's motives seem hazy; perhaps he did not know himself what his aims were beyond putting a stop to the Spanish marriage. It is possible that Wyatt intended to put Elizabeth on the throne; indeed, it is hard to see how he could have envisaged any other outcome in the event of Mary's removal. There is some suggestion that he wanted to marry Elizabeth to Edward Courtenay.
Whether Elizabeth herself knew of Wyatt's intentions is another matter. It was certainly politically expedient for her to not know, so that she could deny involvement should affairs to go to plan. It seems unlikely, though, that she was completely unaware of Wyatt's plans.
There was little popular support for Mary and her Catholic leanings, but even so, Mary was not so secure on the throne that that she could be assured of victory. Wyatt, on the other hand, was counting on the citizens of London to rise up and join him in his rebellion. The first troops sent against him deserted to his cause, and Wyatt must have hoped that his rebellion would succeed against the odds. But Mary did not sit meekly waiting to see what he fate would be; she went in person to the London Guildhall and exhorted the citizens of the city to come to her aid. Twenty thousand men volunteered to act as militia against the insurgents.
Wyatt's men entered London on 3 February, 1554, but the expected outbreak of popular support did not materialize, perhaps in part because of Mary's appeal to the Londoners. Wyatt had a minor skirmish with a troop of infantry at Hyde Park Corner on 7 February, and though he escaped, the morale of his men was dropping rapidly as the promised popular support was nowhere to be found.
Wyatt reached Ludgate on the morning of 8 February, but the gate was shut against him and he had no means to break through. He retreated as far as Temple Bar, where he finally gave recognized that his cause was lost and he surrendered.
Wyatt himself was taken to Whitehall, and thence to the Tower of London. Wyatt was tried for treason on 15 March, found guilty, and executed on Tower Hill on 11 April. Before he died Wyatt was put under extreme duress to implicate Elizabeth in his plot, but this he strenuously denied to the end. In his final address to the crowd gathered to watch his execution, Wyatt exonerated Elizabeth and Courtenay, and took the full responsibility for the rebellion on his own shoulders.
Nevertheless, Elizabeth was imprisoned in the Tower of London for alleged involvement in Wyatt's Rebellion. Whether Mary actually believed that her sister had been involved in the plot is another question, but the Rebellion certainly provided a useful pretext for putting Elizabeth out of the way. In the aftermath of the rebellion Mary's advisors were zealous in tracking down and executing conspirators, and alleged conspirators. Many called for Elizabeth to be executed as well, and it is interesting to consider how history would have changed had Mary not resisted those calls.
One unfortunate side effect of Wyatt's Rebellion was that it hastened the demise of the unfortunate Lady Jane Grey. The 'Nine Days Queen', who had been little more than a pawn in the hands of her ambitious father-in-law, was considered at threat to the throne, and was beheaded, along with her husband and her father, the Duke of Suffolk.
Lady Jane Grey
Edward, Mary, and Elizabeth