Having just spotted this article from 2002 by Science Editor Dick Ahlstrom republished in The Irish Times on Wednesday, I was surprised to find my unopened envelope containing the tablets posted out to homes in 2002…..  

THE IRISH TIMES
What are the iodine tablets for and what should we do with them? DickAhlstrom, Science Editor, provides some of the answers
What are these tablets?
They contain iodine, an element which tends to accumulate in the thyroid gland in the neck.
Why was I given them?
They form part of the Government’s National Emergency Plan for Nuclear Accidents. You would take them if instructed to do so by notices on radio and television to protect against radioactive iodine, a substance which sometimes arises in nuclear accidents.
What should I do with them?
They will arrive in a specially marked envelope with six tablets in each envelope. Do not open them, just put them away in a cool, dry place out of the reach of children. They are no use for anything other than a nuclear emergency.
When should I take them?
Only take them in the event of a nuclear emergency and if instructed to do so by radio and television warnings. They only work against radioactive iodine, not other radioactive substances.
How do they work?
They work by “topping up” the thyroid gland with iodine. This blocks the absorption of radio- active iodine if there is any about in fallout after a nuclear accident.
Why don’t I just take few tablets a week?
This would keep thyroid iodine levels high but there is no benefit in doing this other than to protect against radioactive iodine. It is also possible to have too much iodine in the system.
How should I take them and will they make me feel sick?
Take the tablets with plenty of water. They won’t make you feel sick nor are there any side effects if taken at the recommended dosage as printed on the package. Prolonged usage can cause side effects but this is very rare and these packs only represent a single dose.
How much warning will I have and how quickly to they take effect?
News of a nuclear accident, say at Sellafield, would reach us very quickly. If radioactive iodine was released, then how much time we have to react depends on the weather. If the wind is from the west then it will all be blown across Britain, but an easterly wind would bring it to us within a few hours. The tablets would start working more quickly than this.
How long does the protection last?
One dose is expected to provide protection for up to 72 hours. The dose would have to be repeated for the protection to last longer than this.
Will they protect me from all radiation?
No, only from radioactive iodine, and not all accidents produce radioactive iodine. Fallout from a nuclear accident would release other dangerous substances such as radioactive caesium, which could get onto fresh food, into meat and milk and into water supplies. The Government’s emergency plan recommends sheltering indoors and avoiding consumption of contaminated foodstuffs.
Would they protect me from one of these dirty nuclear bombs being talked about on the news?
Iodine tablets would not protect against a dirty bomb unless it produced radioactive iodine and the protection would only be against the radioactive iodine.
How long do these tablets last when stored?
They are good for three years, up to March 2005. They will have to be replaced after that time with fresh tablets. 

SO NOW YOU KNOW: the tablets are long past their effective date!!