The Once And Future Time Lord (Merlin fanfiction): Chapter 1

The title should give you a good idea of what's going on. I should warn you, though, there'll be a few chapters of exposition before anything super exciting happens. Anyway, enjoy!
Chapters: 1 2 3 4 5 6 7 8 9 10

Their friendship had started when they were only 8 years old. Arthur had feigned illness to get out of attending a council meeting (princes of Camelot were trained from an early age), so he had been sent to Gaius. The young boy, Merlin, had watched in awe as the famous child walked in. Of course, he soon found that Arthur was a total prat, and he called him out on this. Gaius raised an eyebrow in warning at Merlin, and Merlin sighed. 

"Now then, sire, what seems to be the problem?" Arthur faked a cough. 

"I feel terrible. I ache all over and my throat hurts. My head hurts, too."

"Ah, then you'll be needing some of this medicine." Gaius went to get a potion, and Merlin grimaced, knowing it was the worst-tasting potion Gaius had. Arthur squirmed away. "What, don't you want to get better?" Arthur sighed. 

"I'm not sick, I'm only pretending to be sick."

"Well then I'll have to send you back to your father."

"Must you? Please don't!" Gaius could not be convinced. 

"Merlin, send Arthur back to the king."

"I know a place where we can hide," Merlin suggested as they walked. 

"You mean I don't have to go to the meeting after all?" Arthur's face lit up. 

"No-one will even know we're there."

"Won't Gaius worry?"

"I told him I would go to fetch some herbs today. I'll come back with some, just to secure my alibi. And I'm sure you'll come up with a good excuse for yourself."

They walked into the forest, until Merlin stopped. "This is where I like to go when I need some time to myself."

"Do you need to be alone often?" Merlin nodded. 

"People are prats."

"Even me?"

"Especially you."

"Oi!" Arthur punched Merlin lightly on the shoulder. Merlin punched him back. They laughed. "I can't be a prat, I'm a prince!" Arthur insisted. 

"Fine then, a royal prat." Arthur rolled his eyes. 

"You know, you have a good sense of humor. For a servant."

"You have a good sense of intelligence. For a prince." That earned Merlin another glare from said prince, but Merlin could tell that they were quickly becoming friends. They kept insulting each other and sharing anecdotes, until finally, it was time to go back. And that was the beginning of the friendship between Arthur and Merlin.