Shepherd-Barron joined De La Rue in the 1950s as a management trainee and grew to become Managing Director of De La Rue Instruments. He conceived the idea for a self-service machine dispensing cash whilst lying in the bath. He was considering the problem of bank opening hours, having turned up at a bank after closing time one day and found himself unable to withdraw money. Shepherd-Barron has stated that he was inspired by chocolate vending machines: "It struck me there must be a way I could get my own money, anywhere in the world or the UK. I hit upon the idea of a chocolate bar dispenser, but replacing chocolate with cash." He pitched the idea to the head of Barclays Bank over a pink gin. The first De La Rue Automatic Cash System machine, called Barclaycash, was installed outside the Enfield branch of Barclays Bank in north London in June 1967. The first person to withdraw cash was actor Reg Varney, a celebrity resident of Enfield known for his part in a number of popular television series. An early deployment of this device outside of the UK took place in Zurich on November, 1967. It was called The DACS machines used cheque-like tokens which had been impregnated with a radioactive compound of carbon-14. The radioactive signal was detected by the machine and matched against the personal identification number entered on a keypad. The short-range beta emission from carbon-14 could be easily detected, and he determined that the radiation hazard was acceptable as "you would have to eat 136,000 such cheques for it to have any effect on you". Initially, a PIN length of six digits was proposed; Shepherd-Barron tested this system on his wife, Caroline, but found that the longest string of numbers that she could remember was four. As a result, four-digit PINs were chosen and as ATMs expanded across the globe, this became the world standard. Withdrawals from the first Barclaycash machines were limited to a maximum of £10, "quite enough for a wild weekend" according to Shepherd-Barron. Shepherd-Barron received the O.B.E. in the 2005 New Year's Honours list for services to banking as "inventor of the automatic cash dispenser". Various rival cash dispenser systems quickly began to emerge. Another Scottish inventor, James Goodfellow, who was working at Smiths Industries, was commissioned by Chubb Locks to work on a new cash machine. Together with Anthony Davies, he developed a new system whereby the user's PIN could be stored on a reusable bank card, rather than on single-use cheques. The system was patented as GB1197183 and US3905461 and was cited by subsequent patents as "prior art device". Goodfellow's PIN system resembled modern ATMs more than Shepherd-Barron's machine. However, Shepherd-Barron's machine was the first to be installed, if only for a few days.
