All I can imagine now is a plate full of the biggest calamari in the world surrounded by a great many green-faced diners. Are such high ammonia levels (meaning indigestible amounts) unique to squid like Architeuthis, or is it just a proportionate ratio thing?
Many species of squid have high concentrations of ammonium ions in their tissues that make them more buoyant (e.g. Taningia danae, Ancistrocheirus lesueuri); others have a coelom within the mantle cavity filled with fluids that have very high ammonium concentrations (e.g. members of the family Cranchiidae). For more info on ammonium in squid, see:
Clarke, M.R.; Denton, E.J.; Gilpin-Brown, J.B. 1979. On the use of ammonium for buoyancy in squids. Journal of the Marine Biological Association of the United Kingdom 59: 259–276.
A quick word of advice. Get to the BMNH as early as you can, find the Darwin Centre and book yourself on a tour. Only a dozen or so people are allowed in every half an hour and it can get busy sometimes. It can be booked solid by 13:00, and that's without the attraction of the Architeuthis. You can spend the intervening time wandering around that magnificent museum.