Turlough didn't pick up a cider habit at Brendon. The drinking experience of the boys there was generally limited to telling the difference between Cava and Champagne, and such equally useful manifestations of social etiquette. It was only once he had become acquainted with the tramps who hung around town, and learned that, if he smiled and nodded in the right places in their ridiculous stories, they could be quite obliging with the old fermented apples. He carried on the habit in his travels. Having only ever drunk under cover of darkness, Turlough was surprised that the harsh lighting of the TARDIS showed a deep flush brought to his skin by drink, clashing terribly with his hair. Thankfully, only Tegan was there to see.
"I've got a theory about the Doctor," he announced, correctly parsing a sentence quite the acheivement while he was still using both his hands to keep his head upright.
"Really," she said, with an un-critical giggle. She wasn't a bad sort to be around, once her blood chemistry was ever so slightly altered.
"You know how he's so ridiculously British, without being actually..."
"From Earth whatsoever?" she finished for him, helpfully.
"Now, this could have something to do with, shall we say, 'British Culture," he said, referencing something Tegan would only know about if she had ever scoured the back pages of cheap newspapers for amusingly worded adverts for male, female, and all the other sorts of prostitutes. Which, of course, Turlough had never done. Tegan just stared at him blankly (or she tried to, managing about five inches left of his actual face).
"Not forgetting that his newest body was brought about by a sauve old mate of his he has no problem with calling 'The Master'...who often takes it upon himself to threaten the Doctor with something that looks a lot like a...thingy..."
"A sex toy," said Tegan, nodding and completely missing the point.
"All of this coupled with the fact that the Doctor has the physical appearance of your average, easily defilable choirboy," said Turlough, his eyes glazing over. Tegan began to catch onto where he was going.
"He does have a...a tendency to look like a kicked puppy..."
"I think it's entirely possible that the Doctor's a 'sub'," announced Turlough. Tegan recognised the word from a few illicit trips to Soho, and the glint in the Trion's eyes from whenever he or the Doctor were tied up and leered at by Naughty Villain Types. Or that time Turlough had grasped the concept of Poundland.
"And I think," she said, the cider granting her wisdom beyond her years, "The wish is the father of the thought."