Perhaps it is because we now find ourselves confronted by a pandemic and climate change, and relying greatly on original thought, and scientific innovation, that Turing's values and achievements resonate so strongly with us today. Banknote character ‐ speech by Andrew Bailey | Bank of England  Page 2  Banknote features And we’ve tried to reflect those many achievements on this new note, which I’m very pleased to now unveil. Turing is perhaps best known for his code breaking work at Bletchley Park during World War Two. Here, far from being the solitary genius he is sometimes caricatured as, Turing led a team of codebreakers who designed a machine which could be used to decipher German military codes, something once thought impossible. This machine was known as The Bombe, and the technical drawings for it are featured here on the note. Until Turing and his colleagues invented this machine, British Intelligence had employed codebreakers to crack these German cyphers manually. But the sheer complexity of the codes meant they had little success. The early computers which Turing helped design would decipher some of these codes in as little as 15 minutes, giving the allied forces an invaluable military advantage. Historians have credited this work that Turing led at Bletchley Park, with shortening the war by as much as 2 years, saving many millions of lives in the process. But Alan Turing’s contributions to the field of computing start even before his wartime efforts.
In 1936, he wrote his seminal work “on computable numbers”, and this research formed the basis for modern day computer algorithms. We can see some of the calculations from his paper in this table on the new bank note. In his research, he demonstrated how, what he called universal machines, could perform any solvable computation they were presented with. Of course, these universal machines are what we now call computers. Quite simply, his mathematical research in 1936 laid the foundations for modern computer science. After the war Turing returned to computing, but this time helping turn it into reality. Moving to Manchester to work at the National Physical Laboratory, he dedicated the next few years to designing the UK’s first electronic stored program computer. And here is an image of that invention, along with the diagrams Turing drew when designing it. The ACE Pilot machine, although much larger than anything we would use today, was one of the world’s first computers. Recognising the potential for computers to revolutionise the world around us, Turing delivered his now famous quote, when describing the ACE Machine. “This is only a foretaste of what is to come, and only the shadow of what is to be”. He has turned out to be prophetic. And this is reflected in one of the key security features of the note – a two colour foil featuring a microchip image over the main see-through window. Within this are two gold foil squares, which change between a pound symbol and the number “50” when tilted.