Mr Harkin, who has more than 3,000 sheep at his farm in Donemana, Co Tyrone, Northern Ireland, covered them in orange dye to combat the rustlers.
The colour was applied after the problem had reached crisis point.
"Over the years I have lost upwards of 300 sheep to the rustlers. The normal sheep markings did not do any good as a deterrent," he said.
So he decided to try bright orange dye instead. "At the start of the lambing season I lost more than 50 sheep in a single night and I decided drastic measures were needed."
However, the crime-busting move was not immediately successful: when rustlers struck again, it was the middle of the night and they could not see the dye. They made off with the sheep - only to abandon them the next morning.Reuse content