i don't think he is curmudgeonly, but quite funny, a dry wit, and doesn't suffer fools gladly. Fiona had her work cut out though, but overall he came across as a very intelligent man, and the press do bait him a lot, as you can see from the footage.
Suspect also though he would have preferred at least for a time to stay in the Navy, and anyone who has lost a loved career will tell you how hard that is to give up. He has served the Queen all this time, and done a remarkable job. How many men would be second string to their wives for 60 years, very few i would think.