Official photo
An "official" photo (taken in May 2015) of Duncan is presented here:
(click image for full-res 1.7mb)
Copyright / Licence:
This photograph was taken in May 2015 by Matthew Fowler.
If Duncan is writing for your (print or online) publication, contributing to any other type of media, including TV / online video / etc., or speaking at your conference then you may use this photo as part of that engagement.
Otherwise, it is offered under the following Creative Commons License:
This work by Matthew Fowler is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
If you want to make use of this photo which isn't covered by the first point, and you cannot work with that Creative Commons License, then please email matt@duncancampbell.org to discuss.