I read the transcript with interest, noting the following:
The media have totally misrepresented this one.
It turns out I am quite well acquainted with the Board President. It would be difficult to meet a more reasonable and intelligent man.
The time the gun spent in the Iraq box was effectively dismissed. They picked upon the fact that he must have been aware of its existence when he transferred it to a different hiding place some time later.
It was the ammo they were most concerned about in terms of knowingly breaching regulations, and the fact that all the items were stored insecurely, so any casual thief could have obtained them.
"Parliament has decreed" the required minimum sentence was 5 years except in exceptional circumstances. The board found enough exceptional circumstances to award him 18 months, and no reduction in rank or dismissed the Service.
I would suggest that the Board used all the wiggle room they had in sentencing. Use of the phrase "Parliament has decreed" might be a way of saying "Over to you, LCJ"