In reply to TeeBee:
> .......... I figure a bit of 'fresh' tuna in olive oil can do wonders for morale.
Asda do sachets of tuna, which although relatively expensive would be lighter for carrying than tins and get round the tin-opener problems.
Personally I have never yet managed to successively open a tin with a Swiss Army Knife tin-opener, but find the one on my Leatherman OK to use.