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 OBE 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. Personal life In 1953, he married Caroline Murray, the daughter of Sir Kenneth Murray, one-time chairman of the Royal Bank of Scotland. They had three sons. One, Nicholas Shepherd-Barron FRS, is professor of algebraic geometry at the King's College London. Death John Adrian Shepherd-Barron died on 15 May 2010 after a brief illness at the age of 84 in Raigmore Hospital, Inverness, Scotland. He was survived by his wife and their three sons, and extended family. References External links With photos of the Barclaycash tokens and machines 1925 births 2010 deaths Scottish inventors British inventors Officers of the Order of the British Empire People educated at Stowe School Alumni of the University of Edinburgh Alumni of Trinity College, Cambridge Royal Artillery officers British Army personnel of World War II People from Shillong British people in colonial India People associated with Shillong