"So I'm working for pay two days a week and giving the rest of my time to other projects."
Hartley came to New Zealand from Britain via spells living in Sudan and Zambia, giving him an interest in the problems of the developing world and an awareness of the work of Bangladeshi economist Muhammad Yunus.?In 1976 Yunus created the Grameen ("rural village") Bank as an action research project aimed at creating a credit system that would give the rural poor access to banking services and end their exploitation by money lenders.
It is now a multi-billion dollar industry, with hundreds of such banks around the world.
"What microfinance does is give poor people a tool we take for granted," Hartley says.
In 2003, when World Vision was refocusing its development work, it asked Hartley to do some pro bono work for VisionFund Cambodia, which at the time it had 5000 clients. It now has 130,000.
That got him hooked - a development project that was also a financial institution, which could use his particular skills.?Raising funds for VisionFund led him to start Bankers with Vision, which allows people with banking and financial services expertise to volunteer.
It's a small group based in Singapore, which is close to where its people are needed for short but intense assignments.
"In the financial services industry in Asia there is a strong focus on corporate social responsibility, but there is only so much litter people can pick up on a beach.
"Bankers with Vision allows them to use their skills on assignments like helping an institution in Cambodia with treasury functions, or overhauling credit collection in Indonesia," Hartley says.
Microfinance now accounts for more than 10 per cent of World Vision's work, with US$380 million in loans to more than 700,000 borrowers. This year World Vision New Zealand is supporting the growth of Tanzanian microfinance provider SEDA, which Hartley visited last May.
"It's an interesting organisation. It's partnering with World Vision Tanzania and an insurance company to upskill farmers and provide them with crop insurance so they can mitigate their risks and have a better chance of success," he says.
For more information visit worldvision.org.nz
The Vision Fund numbers
US$361m: loan portfolio 2011 financial year
688,000: active borrowers
US$428: average loan
68 per cent: female clients
95.5 per cent: repayment rate
2,722,000: children impacted