I will look into the tuna packets and jerky suggestions. Maybe I can get some biltong or jerky at LHR on my way through. Since I won't have access to a pocket knife (it was confiscated one day last year when I forgot to take it out of my handbag before a flight), that could be a good finger food option.

Sorry, sowalsky, but I will pass on the MREs. I can't imagine where I would get hold of them, in any case. I'm guessing they take up a lot of suitcase room, too.

Thanks to all for the suggestions on how to avoid the dreaded Power Bar. I spent a lot of time in Zimbabwe gnawing on rusks for sustenance, and I do not wish to recall that experience.