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Premium bonds winners June 2018: who chooses the lucky numbers?

Find out everything about the NS&I's number generator ERNIE

The two jackpot winners of the premium bonds prize draw have been announced, taking home £1 million each – but how does the NS&I arrive at the winning bond numbers?

This month, women from the Essex and Hereford & Worcester areas were greeted with the life-changing news that they had won £1 million each in the premium bonds draw.

Here, we reveal this month’s jackpot winners and explain how the winning numbers are chosen.


June 2018 premium bond winners

This month’s jackpot winners are two women – one from Essex, and the other from the Hereford & Worcester area.

The Essex winner had invested the maximum of £50,000 in premium bonds, and bought the winning bond (217JE297574) in January 2014.

The other winner had £27,500 invested, with the winning bond (159QP769919) bought in September 2009.

In total, 3,063,406 prizes were given out in June’s prize draw, with a value of over £87,562,300.

Find out more: premium bonds

How are premium bonds winners chosen?

Every premium bond has an equal chance of winning a prize. Winning bonds are chosen at random from the total pool each month.

To ensure the decision is truly random – and not influenced by bias, or based on a pattern – the NS&I uses a random-number generator, known as ERNIE.

ERNIE – which stands for Electronic Random Number Indicator Equipment – generates a list of numbers each month. These numbers are then matched in order against eligible bond numbers to produce winners.

How does NS&I ensure the numbers are random?

ERNIE is not technically a computer, meaning it doesn’t use a program to generate its numbers. Programs are based on algorithms, which could create patterns or be open to tampering.

Instead, ERNIE chooses its numbers based on an external occurrence – the current version of ERNIE relies on thermal noise made by transistors to inject an element of randomness into its calculations, according to a report in New Scientist.

ERNIE is not connected to any type of network, meaning it’s not possible to hack into it.

Each month, the randomness of the draw is checked by the Government Actuarial Department (GAD), which operates independently from the NS&I. Until GAD provides certification that, to the best of its knowledge, the draw is random, no prizes can be awarded.

When was ERNIE created?

The original ERNIE was built by a former Bletchley Park code-breaker in 1956 to coincide with the launch of premium bonds in November. By the end of the first day of sales, £5m worth of bonds had been bought.

Premium bonds was one of the largest prize draws of its time. In the first draw, on 1 June 1957, some 23,000 prizes were awarded, including a jackpot of £1,000.

Until then, random prize draws had been mainly conducted by pulling balls from a raffle drum. The volume of prizes required a new approach to picking winners, heralding the birth of ERNIE.

Over the years, ERNIE has become more sophisticated and new versions have been created to incorporate new technology.

Today’s version – ERNIE 4 – can complete a draw within seven hours. While this is slightly longer than previous versions, it’s also generating four times as many numbers as ERNIE 3 at its peak.

Version Dates active Prizes generated Time taken to complete final draw Numbers per hour
ERNIE 1 Jun 1957 – Jan 1973 8,067,575 10 days 2,000
ERNIE 2 Feb 1973 – Aug 1988 22,740,704 5.5 hours 65,000
ERNIE 3 Sep 1988 – Mar 2004 77,885,566 5.5 hours 330,000
ERNIE 4 Apr 2004 – present 293,777,959 7 hours 1,000,000

Source: NS&I, correct as of 31 May 2018

Why do some results seem biased?

Looking through the list of winners, it may seem as though ERNIE favours certain regions more than others, or that specific numbers win more often.

This year alone, three jackpot winners have all been from Wiltshire. So is something suspicious going on?

In fact, it’s entirely possible for a truly random draw to repeatedly feature the same numbers, or winners from the same region. Random means just that – there is no pattern or guiding principle behind the selections.

Every bond in every draw has an equal chance of being chosen, which also means that previous winners have no bearing on what’s chosen next time around.

Another factor is that premium bonds are not distributed evenly across the UK. People living in the south tend to hold a higher number of bonds, so it’s unsurprising that these regions feature frequently among the winners.

Another rumour persists that only newly issued bonds win prizes. But the number of bonds bought has sky-rocketed in recent years – recent stats from the NS&I show that 89% of eligible bonds have been bought since 2000.

That said, premium bonds don’t expire and continue to be entered into the draw. In July 2004, a bond first purchased in 1959 for just £3 won the £1m jackpot.

So while you may believe you can spot a pattern, or that there are ‘lucky numbers’, it all comes down to luck of the draw.

You can find out more in our guide to premium bonds.

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