The previous relationship Day developed with Jordan at Telefonica will benefit their new own at Sainsbury's, and gain structural support from his strategy on how the CIO and CDO should generally work together.
"I think probably the most important thing is very clear terms of reference," he says. "The relationship has to be absolutely hand in glove, and understanding who does what, where the hand-offs are, what you do for each other, and where you support one another is probably the most important thing.
"So set clear boundaries in the initial instant so you understand who's responsible for doing what. I think most importantly, the role of a CIO and the role of a CDO are very different, but they come together in the technology space in that a CIO is clearly all about technology and a CDO needs to understand technology as an enabler for doing what we do for from an analytics perspective.
"At Sainsbury's, it's a new role so we're working through how we work together. But one of the things that are absolutely clear from the time I've been in the business is that the business is massively collaborative, so it's actually very easy to work out how you do stuff."
Embracing that culture of collaboration was crucial in Day's first few months at the company. In his first six months, the new CDO spent time meeting more than 200 people from the supermarket, bank and Argos arms of the vast organisation. Many had worked for the company for decades, and their wealth of experience opened his eyes to a range of opportunities.
He had taken a year off work after leaving his role of CDO and Business Intelligence Officer at News UK. A session with a coach led him to draw up a list of three organisation where he would like to work based on his personal priorities, one of which was Sainsbury's. As luck would have it, within weeks the company called and invited Day in for a meeting.
Day was blown away by the opportunity and the fit with what I was looking for in a job," and cut his break short to start a new job.
He was most excited by the vast quantities of data in Sainsbury's divided into three streams: customers, colleagues and commercial
"We're a business with loads and loads of data," he says. "We have 191,000 colleagues, which is more colleagues than some organisations have customers. We have loads and loads of products and we have millions of customers.
"I saw an opportunity in data to transform the organisation."
Starting the new job
In his induction he was told he would need to show his passport. He didn't have it and was told he'd have to return home to retrieve it before starting. Day was irritated as it could make him late for his first meeting with CEO Mike Coupe, but happy to have evidence of the company's egalitarian culture.
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