Who did Queen Elizabeth I appoint Chancellor in 1587?

Good question, Frankie!

You are referring to Sir Christopher Hatton, (born 1540, Holdenby, Northamptonshire, Eng.—died 1591, London). Hatton played a prominent role in the examinations of various Catholic plotters against the Elizabeth I. As you rightly pointed out, he was commissioner for the trial of Mary, Queen of Scots, in 1586. Hatton also strongly supported the current archbishop of Canterbury (John Whitgift) against the Puritans. Elizabeth’s desire to see Whitgift and Hatton work together may have actually contributed to Hatton’s appointment as lord chancellor in 1587.