From a Special Operations officer quoted in Tom Ricks’s Inbox (The Washington Post: 5 October 2008):
One of the most interesting operations was the laundry mat [sic]. Having lost many troops and civilians to bombings, the Brits decided they needed to determine who was making the bombs and where they were being manufactured. One bright fellow recommended they operate a laundry and when asked “what the hell he was talking about,” he explained the plan and it was incorporated — to much success.
The plan was simple: Build a laundry and staff it with locals and a few of their own. The laundry would then send out “color coded” special discount tickets, to the effect of “get two loads for the price of one,” etc. The color coding was matched to specific streets and thus when someone brought in their laundry, it was easy to determine the general location from which a city map was coded.
While the laundry was indeed being washed, pressed and dry cleaned, it had one additional cycle — every garment, sheet, glove, pair of pants, was first sent through an analyzer, located in the basement, that checked for bomb-making residue. The analyzer was disguised as just another piece of the laundry equipment; good OPSEC [operational security]. Within a few weeks, multiple positives had shown up, indicating the ingredients of bomb residue, and intelligence had determined which areas of the city were involved. To narrow their target list, [the laundry] simply sent out more specific coupons [numbered] to all houses in the area, and before long they had good addresses. After confirming addresses, authorities with the SAS teams swooped down on the multiple homes and arrested multiple personnel and confiscated numerous assembled bombs, weapons and ingredients. During the entire operation, no one was injured or killed.
By the way, the gentleman also told the story of how [the British] also bugged every new car going into Northern Ireland, and thus knew everything [Sinn Fein leader] Gerry Adams was discussing. They did this because Adams always conducted mobile meetings and always used new cars.
The Israelis have a term for this type of thinking, “Embracing the Meshugganah,” which literally translated means, embrace the craziness, because the crazier the plan, the less likely the adversary will have thought about it, and thus, not have implemented a counter-measure.