The logic of this may seem a bit difficult to grasp. Let me try to help:
On 7th November 2012 Nightingale was sentenced to 18 months immediate custody after pleading guilty to the two possession offences.
On 20th November a special debate on the matter took place in the House of Commons. (I’ve no idea why an individual conviction and sentence should be the subject of a Commons debate, but there you go).
On 29th November the Court of Appeal reduced the imprisonment term to 12 months and suspended it. Nightingale was released.
On 13th March 2013 the Court of Appeal overturned his conviction (of 7th November) on the grounds that he had been put under undue pressure by the judge to plead guilty. They ordered that the original conviction be quashed, that Nightingale be allowed to re-enter his plea and that, if necessary, a trial should be held..
On 2nd July, following a Not Guilty plea, Nightingale’s trial began. On 10th July he was convicted by the court martial board and on 25th July he was handed the suspended sentence. It is the Court of Appeal’s decision on 29th November which Judge Jeff Blackett, the Judge Advocate General, felt constrained by in handing out the suspended sentence. The Court of Appeal had already heard all the evidence of the case and presumably nothing new was introduced at the trial. Whilst it is true that there was nothing to prevent him handing down an immediate custodial sentence it was clear to him that had Nightingale appealed the sentence would almost certainly have been reduced.
Interestingly, throughout all of this, there have been no howls of anguish from those who oppose trials without a jury. mac has already pointed out some of the deficiencies of the Court Martial system.