Here's the correct info (! Amazing how one's memory modifies facts.. well.mine did!)
The song Come By was composed by Steve Knightley after a conversation with John Wright (who was a shepherd in the Scottish Borders, and previously in N England)
It was based on what happened after the Chernobyl disaster, the clouds of contamination affected the Borders so badly that livestock and wild deer were not allowed to be eaten - this went on for many years, and I believe there are still areas that react to geiger counter? I am not certain, but assume much of the domestic stock would have been culled? Hence no work for shepherds or their collies?
I don't recall.much publicity at the time, but I expect there would have been some governmental covering up so as not to cause panic?
What year was Chernobyl? I recall it was May, must have been about 1986? Shall check.