(A Doctor Who/Discworld Crossover)

With deliberate care, Vetinari descended the steps, his hand sliding into his cloak as the voices echoed through the tunnel.

“…so, you see, Doctor, if you attach the rotors here and put the alcohol propelled engines there, I think it will work."

“Yes, I can see that, Leo, but don’t you think it might be a little dangerous to attach weaponry to it?”

“Weaponry?” Leonardo de Quirm’s voice sounded bemused. “Whatever do you mean?”

Vetinari halted as there was the rustle of paper. “I mean these, Leo.” The voice was gentle, almost cajoling, as if the stranger was talking to a child…and, in a way, maybe he was.

“Ah, you mean the automated lead pellet firing mechanism? But, my dear Doctor, those aren’t weapons, they’re purely for clearing the airspace for flight, there are a lot of wild swamp dragons in the area you know, couldn’t have them getting snarled in the engines!”

“Ah…I see.”

Vetinari grimaced as his hand curled around his dagger. Leonardo De Quirm was undisputedly one of the finest geniuses of this age, but in matters of the world he was remarkably naïve; which was why he kept him safely ensconced in the bowels of the palace, away from those who would take his designs a step beyond the drawing board. Silently, he sped down the tunnel towards the door and tested the handle. It was locked.

Vetinari frowned. This was the only entrance into Leonardo’s quarters, yet the stranger found a way inside. A wizard, perhaps…but what would a wizard want with Leonardo’s designs? He slid the key into the lock and turned it, opening the door a crack…

“I always enjoy your little visits, Doctor, they’re so illuminating,” Leonardo said, his voice cheerful as he poured the stranger a cup of tea. “Havelock tries to visit as much as possible, but his mind is usually concerned with matters of state.”

“Ah, yes, Havelock is your patron, isn’t he?” the peculiarly garbed figure said breezily as propped his feet on the table and took a sip out of his cup.

“The best one I’ve ever had,” Leonardo said cheerfully. “Never bothers me about my projects, just let’s me carry on and keeps me in supplies, fine chap!”

“Hmm,” amusement coloured the stranger’s voice. “No doubt he is…and I’m sure he keeps a complete record of all your ideas.”

“Locks them up safe and tight…can’t be too careful when it comes to patents, you know.”

“Indeed.” The stranger said as he placed his cup on a small clear space on the table. “Well, it’s been nice catching up with you, Leo, we must do this again soon.” The stranger bounced to his feet energetically, and grinned widely.

Vetinari raised an eyebrow as Leonardo’s face fell. “So soon?”

“I’m afraid so, old chap. You know how it is.”

Leonardo nodded reluctantly. “I still have rather fond memories of our travels…of course, I’m not as young and spry as I once was…”

“Nonsense,” the stranger said, giving Leonardo a one armed hug. “And maybe one day we’ll do it again; but, for now, I think this may be the perfect place for you to be… and I think your patron might agree. Don’t you, Havelock?”

A strange feeling rose in Vetinari’s chest, and it took him a moment to recognise the sensation as surprise. It wasn’t a feeling he was well acquainted with. Slipping the dagger back up his sleeve, Vetinari straightened and let the door fall open. “You have me at a disadvantage,” he murmured, quelling the uneasy thought that this was actually true. “You know my name, but I don’t know yours…?”

“Ah, well, hardly surprising, that,” the stranger amiably. “After all, it is kind of difficult to visit Ankh-Morpork and not know your name…oh, I’m the Doctor, by the way.”

A hand was thrust in front of him, and Vetinari eyed the Doctor’s wiggling fingers. Even the man’s handshake was full of restless energy. From the corner of his eye, he noticed the eager smile on Leo’s nodding face, and gave into the inevitable. Disappointing Leonardo was not unlike kicking a puppy, and he was rather fond of dogs.

He shook the Doctor’s hand.

“Well, that’s my cue to leave, I suppose,” the Doctor said brightly. “Nice meeting you, Havelock. Take good care of my friend, will you? I wouldn’t like anything bad to happen to him.”

Vetinari rolled the Doctor’s words around in his mind as he caught his eye. Taken at face value, they were innocuous enough, but the Patrician recognised an unspoken threat when he heard one…and something told him that Doctor didn’t make idle threats.

“Oh, Doctor, don’t be such a worrywart,” Leonardo, boomed cheerfully. “How could I be in any danger? I’m just a poor, befuddled artist. Who’d want to harm me?”

Once again, Vetinari’s eyes met the Doctor’s and a glimmer of understanding ran between them.

“Yes, well,” the Doctor said eventually as he bounced over to a large blue wooden box, which had somehow managed to blend into the background, in the corner of the room. Vetinari idly wondered if it was another sapient pearwood artefact; it had that look about it. “See ya soon, Leo.”

Vetinari watched as Leonardo gave the Doctor a sad little wave as he disappeared into the box and discreetly cleared his throat. “An old friend?” he ventured.

“Oh yes,” Leonardo said cheerfully. “He’s a scientist, you know. A real one, mind, not a mere dabbler, like me.”

“Indeed,” Vetinari murmured and he watched bemusedly as a strange, rather eldritch, boom emanated from the box, as it slowly dematerialised in front of his eyes.

“Ah,” he said. “Definitely sapient pearwood, then."

And Leonardo gave his benefactor a knowing smile that was strangely at odds with his usual, naïve nature.