William Herle was a pirate and spy who was imprisoned in the Marshalsea

Marshalsea

The Marshalsea was a prison on the south bank of the River Thames in Southwark, now part of London. From the 14th century until it closed in 1842, it housed men under court martial for crimes at sea, including those accused of "unnatural crimes", political figures and intellectuals accused of...

 prison in 1571. He became known for his part in Elizabeth I's intelligence network inside the jail, smuggling letters to William Cecil

William Cecil, 1st Baron Burghley

William Cecil, 1st Baron Burghley , KG was an English statesman, the chief advisor of Queen Elizabeth I for most of her reign, twice Secretary of State and Lord High Treasurer from 1572...

, Lord Burghley, about people involved in the so-called Ridolfi plot

Ridolfi plot

The Ridolfi plot was a plot in 1570 to assassinate Queen Elizabeth I of England and replace her with Mary, Queen of Scots. The plot was hatched and planned by Roberto di Ridolfi, an international banker who was able to travel between Brussels, Rome and Madrid to gather support without attracting...

, a Roman Catholic plan to assassinate the Queen and replace her with Mary, Queen of Scots.