In 1399, he successfully led a group of barons in revolt against King Richard II, who was deposed. Henry seized the English throne for himself and Richard was imprisoned in Pomfret Castle where, having been denied food on the orders of the Archbishop of Canterbury Thomas Arundel, he starved to death in 1400.
In the same year, there was a failed attempt to assassinate him in Oxford. Shortly afterwards, Henry released Richard's wife Queen Isabella from her captivity in Sonning Palace. He hoped that she would marry his 13-year-old son Prince Hal. However, she had no intention of doing so, describing the prince as "a spotty boy".
He did not approve of many of the violent and murderous tactics employed by Arundel.