It appears that Suffolk resold the wardship to Sir Thomas Wyndham of Felbrigg, another friend and colleague of Knyvet's father.

Knyvet joined his uncle, Thomas Howard, 3rd Duke of Norfolk, in suppressing the uprising in Yorkshire in 1536 known as the Pilgrimage of Grace.

According to Virgoe, Norfolk 'always wrote about Knyvet in terms which revealed small sympathy for his hotheaded, conceited and clever young kinsman'.

In April 1541 Knyvet struck Thomas Clere, a servant of the Duke's son and heir, Henry Howard, Earl of Surrey, in the King's tennis court.

In February 1542 Knyvet was also bound in 500 marks to attend daily before the Privy Council, although for what reason is unknown.

Knyvet contributed to the downfall of the Howards in 1546, and testified against Surrey at his treason trial in December of that year.

However, according to Virgoe, he remained 'a thorn in the flesh of authority', being bound in £1000 in February 1548 to attend before the Protector Somerset and the Privy Council to answer charges which may have been related to his alleged adultery with the Countess of Sussex.