Issued by the Bank of England in 2021, this polymer note is a rare find for collectors. The note features the queen's image on the front, with a variety of security features to deter counterfeiting. The reverse side features a portrait of Alan Turing, with a machine resembling the Bombe that he helped design during World War II. This note is a great way to commemorate the life and work of one of the most important figures in computer science.