‘If everything works, you are not pushing the envelope hard enough… great ideas should fail some of the time’

Clive Humby, co-founder of dunnhumby

‘Work hard, believe in yourself, find your opposite (not just for love but for work) and then surround yourself with brilliant people’

Edwina Dunn, co-founder of dunnhumby

Husband and wife Clive Humby and Edwina Dunn – hence, the name of their retail data business, dunnhumby – came up with a brilliant idea. What if you combined those old-fashioned Green Shield stamps, where you licked hundreds of stamps into a book to afford, say, a kettle, with a personalised record of what you’d actually purchased.

In exchange for giving the supermarket your shopping history, the understanding was that they would give you special offers and discounts.

However, back in the early Nineties, none of the supermarkets really had any idea of what their customers bought.

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In 1994 Tesco, which was the second-most popular supermarket after Sainsbury's, wanted to create a new loyalty card. The Tesco executive in charge of developing the Tesco loyalty card heard computer scientist Clive Humby speaking at an event and approached him afterwards.

Tesco agreed to trial the dunnhumby-engineered Clubcard for three months across nine stores that same year, after which the team were asked to present their findings to the Tesco board. A gulp-inducing moment. At the end of the presentation, it was Tesco's then-chairman Lord MacLaurin who broke the awkward minute-long silence. He said, “What scares me about this is that you know more about my customers after three months than I know after 30 years.”

In just over a year it enabled Tesco to overtake Sainsbury's and become the UK's largest retailer.

With Tesco's blessing, dunnhumby was soon signing similar deals with supermarket groups around the world, and then in 2002, Tesco bought a 53 per cent stake in the business.

In 2010, Clive Humby and Edwina Dunn eventually sold the remainder of the business to Tesco, pocketing a widely reported £93m in total.