It was an excellent idea, but I did feel that it went astray at times. Gareth seemed not to understand that one of the things that keeps these service people going is a sense of a team all working together. This was reflected in the way the original group of 10 worked well together as a choir - it reproduced the camaraderie of service life.
But them, seemingly randomly, Gareth introduced two extra singers, which was a very strange thing to do, both socially and vocally - it was obvious from the start that the choir was too small - with a group if untrained and inexpert voices the more the merrier when it comes to producing a good sound. And, worse still, he dropped a whole gang of US singers on them at the last minute. It seemed a bit crass to me - the choir should have been told that this was the plan to start with, so they could have welcomed their fellow singers from the US with enthusiasm. It felt a bit manipulative to me.
I also felt that (like most "reality" shows) Gareth was pressing people's buttons to make good TV - almost encouraging them to bare their souls and break down - I felt uncomfortable about that. It seemed slightly disrespectful - and I admired the head injured man who was clear that he did not want to be misrepresented in a mawkish or unrealistically "happy ending" way.
It was very interesting to see the woman who did the starting solo - excellent voice and lots of courage.
The end product eventually worked well; but I was not quite so happy with the process.
I have run choirs for people of all sorts for most of my adult life and have seen how transforming they can be for everyone, and particularly for those with MH problems. And it was clear that singing at Invictus was very therapeutic for many.