Melinda Gates discusses her fight against global poverty.

But as she has become more expert on the issues the foundation is embracing, Gates has come to understand her own influence and the role she can play as an advocate. To build more support for their causes, Gates has accepted more media interviews, though with some reservations. She cringes at being trailed by a camera crew, or any spectacle that draws attention to herself instead of her work. In our meeting, she is both open and a bit guarded.

Still, she is at ease talking about her marriage. Gates speaks of her relationship with her husband in a way that reveals an equal partnership, a true collaboration. They have matching, adjoining offices at the foundation, connected by a narrow, private doorway. Sometimes Bill eats lunch at the small, round wooden table in her office, even when she isn’t there.

Sitting at that table, overlooking a residential Seattle neighbourhood and sipping a glass of iced tea with lemon her assistant laid out for her, Gates repeatedly begins sentences with “Bill and I…”

She describes many hikes and walks spent talking about the vision for their personal and professional futures. “It was a great time for us to brainstorm and strategise about what we wanted. Later [the focus] became our family life, but now it’s the foundation,” she says. “I can’t tell you how many walks we’ve taken on the beach talking about agriculture or health tools.”

Even when they were both at Microsoft, the couple prioritised time away together. “People were always surprised. They’d say to me, ‘Do you do email during vacation?’” she says. They didn’t. Instead, they would work furiously on the plane, download once they reached the hotel, then shut off their computers completely for a full week. “We’d read the same books at the same time, then we’d discuss them together,” Gates says.

Today, Gates still makes sure that she and her ­husband continue to get this quiet time. Particularly after a trip abroad on foundation work, she insists that they have a free day together before going back to the office. “Otherwise, you can come right back to your life here and you don’t get to talk about or think about what you’ve learnt together on the ground,” she says.

The couple also balance each other out on the public front. While her husband has remained the perpetual geek, focusing on technology developments at the foundation, sometimes in blunt or polarising terms, Gates has brought a human element to the face of the foundation. “Melinda has a reputation of being a really thoughtful person,” says Stacy Palmer, editor of The Chronicle of Philanthropy. “When they travel, she’s the one looking so intently at the people she’s talking to. She really relates to the human side.”

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Melinda Gates is not only shifting the image of the foundation towards the human, but also its core philanthropic strategies. Traditionally, the Gateses have focused on applying their scientific might to­ developing breakthrough technologies such as drought-resistant maize and HIV vaccines.

But most recently, Gates has been redirecting part of the foundation’s resources to social science. In October, she hosted a conference on “behaviour change,” inviting the world’s top academics on the subject to meet with top health advocates, including the ministers of health from Ethiopia and Ghana, and talk about how to ensure people actually use the technologies the foundation is delivering.