The first quarter of 1549 was a difficult time for Thomas Seymour. He had been accused of attempting to kidnap the King, his nephew, from Hampton Court Palace. It was the evening of 16 January and it was also alleged that Seymour killed the King’s dog while attempting the kidnapping.
There are only two accounts (that I’ve discovered) of the events. Neither of the accounts were written by anyone notable or anyone who wasn’t an ambassador. The first account was by François van der Delft, who was the Imperial ambassador on 27 January 1549:
Sire, I have heard here that the Admiral of England, with the help of some people about the court, attempted to outrage the person of the young King by night, and has been taken to the Tower. The alarm was given by the gentleman who sleeps in the King’s chamber, who, awakened by the barking of the dog that lies before the King’s door, cried out “Help! Murder!”
Everybody rushed in; but the only thing they found was the lifeless corpse of the dog. Suspicion points to the Admiral, because he had scattered the watch that night on several errands, and because it has been noticed that he has some secret plot on hand, hoping to marry the second daughter of the late King, the Lady Elizabeth, who is also under grave suspicion. On my arrival in England, however, I will write the truth more fully to your Majesty, having nothing now to go upon beyond the information given by those who repeat common report.
The other account was written on the 15th of February 1549 from John Burcher, a well-know reformist in Strasbourg to Henry Bullinger, one of the most influential theologians of the Reformation in the 16th century.
From Tudor Nobility, Professor G.W. Bernard states that this letter gives a clue to how Seymours alleged plans were discovered. If, all the events listed in the letter are true then this indeed explains how it all went down.
In “Original Letters Relative to the English Reformation: Written During the Reigns of King Henry VIII, King Edward VI, and Queen Mary : Chiefly from the Archives of Zurich, Part 2”:
The uncle of our king (I do not mean him who we call the protector of the kingdom, but his brother) has attempted, by an unheard of treachery and cruelty, to destroy with his own impious hands, in the deep silence of the night, our innocent king. The tragedy was thus acted. He obtained from one of the king’s chamberlains, who was privy to his design, a key, by means of which there is the nearest access by a door to the royal bed-chamber, which he entered in the dead of night, accompanied by the accomplices of his crime. There was a space between the door at which he entered and the king’s chamber, where was lying hid a little dog, the most faithful guardian of the youth, having been accidentally shut out of the chamber; and when he perceived the assassin hurry towards the king’s chamber door, he betrayed the murderer by his barking. The enraged assassin first killed the dog, and, had not God prevented, would have killed his master also. A faithful guardian of the royal person, roused by the noise, came out, having awakened some of those who from their office are called body-guards. As soon as he beheld with astonishment the murderer at the door of the royal chamber, he demanded of him what was his business there at the very dead of night. the man replied with trembling, that he wished to know whether the prince was safely guarded. But this excuse did not avail him, and on the next morning he was committed to the Tower of London as a traitor; as was also shortly after the king’s chamberlain, who had supplied him with the key by which he gained admission. And unless the king had accidentally bolted the inner door of his chamber, which is done very seldom, it would certainly have been all over with him before that other person could have run to his assistance. Together with the traitor was seized also a certain knights who was the warden of the king’s mint at Bristol, which is the richest sea-port in England. Here then you have the happy issue of this tragedy. They have, I doubt not, suffered at length the due punishment of such wickedness.
The traitor who plotted death of our king was condemned to death on the 12th of March, and there is no doubt but that he will be brought to execution.