£50 GBP 2021 Polymer note

£50 GBP 2021 the front is Elizabeth II

We first issued our polymer £50 on 23 June 2021. It features the scientist Alan Turing.

Features on the new £50 note include:

A photo of Turing taken in 1951 by Elliott & Fry which is part of the Photographs Collection at the National Portrait Gallery.

A table and mathematical formulae from Turing’s seminal 1936 paper “On Computable Numbers, with an application to the Entscheidungsproblem” Proceedings of the London Mathematical Society. This paper is widely recognised as being foundational for computer science. It sought to establish whether there could be a definitive method by which any theorem could be assessed as provable or not using a universal machine. It introduced the concept of a Turing machine as a thought experiment of how computers could operate.

The Automatic Computing Engine (ACE) Pilot Machine which was developed at the National Physical Laboratory as the trial model of Turing’s pioneering ACE design. The ACE was one of the first electronic stored-program digital computers.

Technical drawings for the British Bombe, the machine specified by Turing and one of the primary tools used to break Enigma-enciphered messages during WWII.

A quote from Alan Turing, given in an interview to The Times newspaper on 11 June 1949:

“This is only a foretaste of what is to come and only the shadow of what is going to be.”

Turing’s signature from the visitor’s book at Max Newman’s House in 1947 which is on display at Bletchley Park, where he worked during WWII.

Ticker tape depicting Alan Turing’s birth date (23 June 1912) in binary code. The concept of a machine fed by binary tape featured in the Turing’s 1936 paper.

Two key security features can be checked to help confirm that notes are genuine:

a metallic hologram which changes between the words ‘Fifty’ and ‘Pounds’ when the note is tilted.

a large see-through window with a gold and green foil on the front depicting a finely detailed metallic microchip image.

There are two green 21 spiral features based on a sunflower head (linked to Turing’s morphogenetic work in later life). The foil is silver on the back.

A metallic hologram which changes between the words ‘Fifty’ and ‘Pounds’ when the note is tilted.

A silver foil patch with a 3D image of the Coronation Crown.

The Queen’s portrait in the see-through window with ‘£50 Bank of England’ printed twice around the edge. (The small clover shapes on the outside of the window are based on architectural features at Bletchley Park.)

A smaller see-through window in the bottom corner of the note, the shape of which is based on architectural features at Bletchley Park.

A red foil patch containing the letters ‘AT’ is based on the image of a sunflower head linked to Turing’s morphogenetic work in later life.

£50 GBP 2021 the back is Alan Turing

mathematical table and formulae from Turing’s seminal paper “On Computable Numbers, with an application to the Entscheidungsproblem”;

Automatic Computing Engine (ACE) Pilot Machine (one of the first electronic stored-program digital computers), series of background images with technical drawings from the "ACE Progress Report";

ticker tape depicting Alan Turing’s birth date (23 June 1912) in binary code;

technical drawings for the "British Bombe" (machine used at Bletchley Park to break Enigma-enciphered messages during WWII)