What has, for you, been the most fascinating moment of The Human, Earth Project?
Was it the moment when, after three years and eight months, P returned to her home and family in Vietnam?
Was it when the full complexity of M's situation as a forced bride in China was finally revealed?
For me, the most fascinating moment occurred in November 2012, long before anyone had even heard of The Human, Earth Project.
It was a moment when a long-smouldering concern for an abducted friend ignited a fire in my belly - a determination to act without knowing what I could do, or what the personal cost might be. Everything else that has occurred since then was merely a result of that moment.
There are moments in our lives when we're touched so deeply by tragedy and injustice that it becomes impossible to sit quietly by any longer.
These moments come not with the fury of a charging bull, but with the stubborn tenacity of a mule determined to move the world, if only by a millimetre.
Another such moment occurred eleven days ago, here in the mountains of northern Vietnam, and there's been a fire raging in my belly ever since.
This will be a deeper story, of which M and P and the trafficked girls of this area constitute only a small part. There's no saying yet what form it will take, or where it will lead me.
In the meantime, however, The Human, Earth Project has been branching out in some unexpected new directions.
I've been absolutely thrilled to accept an invitation to the Summit At Sea conference, the major 2015 event of Summit Series, which will take place off the coast of Florida this November.
What's Summit Series?
I remember asking myself only a few months ago - and, when I did find out, I never actually expected to receive an invitation.
I was recently contacted by award-winning crime novelist Belinda Bauer, who cited The Human, Earth Project as an inspiration for her sixth novel, The Shut Eye, to be released in March.
This week the Zero To Travel podcast featured a 22-minute episode on The Human, Earth Project, to which you can listen here.
It's going to be a big year.