King Henry VI is believed to haunt the Wakefield Tower. He was murdered as he knelt in prayer the hour before midnight on the 21st May 1471. If  the rumors were to be believed, the knife that killed him was presumably held by the Duke of Gloucester ( later the infamous Richard III). Every year on Henry’s anniversary of his death, he is said to appear as the clock ticks towards midnight & angrily paces around the interior of Wakefield Tower, once the clock strikes twelve, he fades away into the walls to rest for another year.

Henry VI of England - Wikipedia

The last king of the Lancastrian dynasty, Henry VI (englishmonarchs.co.uk)

BBC - History - King Henry VI

Anecdotage: Henry VI's Ghost at the Tower of London