This was written with Rachel Taylor at Child Soldiers International. I think it was the first thing we wrote together.
By this point (2013) we had gathered enough evidence on the ethical issues arising from enlisting 16 and 17 year olds, and on the feasibility of raising the age to 18, that we could outline the case for change in a report of this kind.
After this report we continued to develop the evidence, on the strength of which there is now widespread support for the armed forces to enlist adults only.
The report is on the Child Soldiers International site, here.