The Oblong Office, 4 Grune, 09h48:
"Drumknott?"
"Yes, my lord?"
"Send a clerk to the Head of the Thieves' Guild and the Assassins' Guild and have him inform them they both have meetings with me. At the same time. I have need of Operation Impossible."
Drumknott froze. "Operation Impossible, my lord?" he repeated, incredulous.
"Yes, Drumknott, a co-operation between the two main guilds in the city." Vetinari reiterated patiently.
Drumknott still looked confused and faintly flustered, an unusual look for the Patrician's ordinarily composed head clerk. He pushed his glasses up the bridge of his nose and continued, "Yes, I do recall what it stands for, my lord, I only ask because… well… those two are the two guilds with the most bitter rivalry. With respect, sir, what could you possibly ask them to co-operate on? The thieves specialise in pick-pocketing, the assassins in inhumation. Where do these spheres overlap?"
The Patrician smiled. It was a sly smile, it was a pointed smile. It meant business. Drumknott wasn't too pleased with the possibly implications thereof. "Ah, but Drumknott, that's not all they do. Aside from casual mugging and pick-pocketry, the thieves also specialise in burglary, and the assassins are all well versed in stealth, lock-picking and breaking and entering without being noticed. You see where this begins to overlap? Every now and again, there are times when you wish to call a Thief for the ends you desire, but an Assassin for the means. Operation Impossible is there for these occasions." he explained idly.
"But the Thieves and the Assassins hate each other! Getting them to work together would be impossible."
"And that's exactly how the operation received its name, Drumknott. Send out the clerks, would you?"
Something about the Patrician's languid tone flashed a warning signal in the head clerk's mind; the discussion was over and as much as he didn't believe the mission would reach a satisfactory outcome, his boss wasn't interested in hearing about it anymore.
"Yes, my lord."