SITUATIONS LIKELY TO RESULT IN A BREAKDOWN IN FOOD AND WATER SUPPLY.
1) FLOODING. Mass immigration to the South-east of England and elsewhere has forced the government to allow the construction of housing on flood planes.
Most survivalist sites seem to be very keen on dry noodles which are only useful if you have water and heat. I prefer to keep plenty of fruit juice in the house. This will keep me hydrated and maintain my strength even if I have no other food.
2) TERRORIST ATTACK. Any use of nerve gas or dirty bomb anywhere will render the water supply suspect. I would recommended having seven days liquid in this event.
3) FLU PANDEMIC. Sweat it out at home in bed. Expect power cuts if it becomes a true pandemic. Drink fruit juice.
Fruit juice emerges as an all purpose survival aid. This will keep at last six months and is far more useful than a Rambo costume with Bazooka and flamethrower or some such nonsense.