Here's the wiki entry on Tom & Katherine Howard (& Lady Rochford)
Culpeper was executed ...at Tyburn on 10 December 1541, and (his) head put on display on London Bridge. Culpeper was buried at St Sepulchre-without-Newgate Church in London. The Queen, Katherine Howard, and Lady Jane Rochford were both subsequently executed on 13 February 1542.
Actually the whole period makes for some interesting if not ghoulish reading, for example, some accounts of the execution of Margaret Pole, The Countess of Salisbury....
"A child of five would understand this. Send someone to fetch a child of five."
1. Adultry was the excuse. Remember, they also accused her of being a witch. She was pretty much executed for being a free thinker -- and not giving the King a male heir. Henry grew tired of her and had a roving eye.