Getting confirmation of how the pattern works – or even whether it does what researchers think it does – is difficult. No one, from bank officials to equipment manufacturers, wants to talk about it. The Bank of England has never commented publicly on the existence of the so-called EURion Constellation. Instead, in an interview, director of banknotes Victoria Cleland explained that the bank has an interest in making counterfeiting as difficult as possible. “If you get a £20 counterfeit note today, it’s worth absolutely nothing,” she explains. “You’ll be £20 out of pocket. So on an individual by individual basis, it’s bad news – and people could lose confidence in the cash they’re using.”

Who came up with the EURion Constellation in the first place? Although they declined to comment for this article, a Japanese firm called Omron was linked to the pattern in a 2005 press release published by the Reserve Bank of India. In January of this year, a blog post apparently written by a retired Indian government official named N R Jayaraman stated that the design, which he called the Omron pattern, has been used on banknotes around the world since 1996. His blog post also stated: “The design and size of the Omron mark shall be as per the master film provided by the SSG-2, the film supplied by the firm itself and should not be altered in any manner, lest the anti-copying feature will fail to work.”

Security ‘doughnuts’

It seems that SSG-2 refers to the method by which the pattern is transferred to banknote paper during printing. In an email, however, Jayaraman said that the specific machinations of the process are not known to him.

A string of public patents provide further evidence that Omron is indeed behind the EURion Constellation. This one, filed in 1995, states that “marks are detected which are arranged in a given spatial relationship in image data printed on, for example, bank notes or negotiable securities.” An image attached to the patent shows a pattern that is conspicuously similar to the EURion Constellation, albeit with the central circle missing.

One person able to shed some light on the pattern is Steve Casey, marketing director for Innovia Films, which manufactures sheets of material onto which banknotes may be printed. “The rings are called ‘doughnuts’ in the industry”, he explains. “It’s one of the first security features that was ever developed for banknotes in the digital era.”