The head was a dead giveaway, so to say.
"Oh, dear," the Doctor rubbed his hands.
"Jamie?"
"Yes, Doctor?"
"I wanted to get ahead of my horse, not his head."
"I know," Jamie replied confidently. "It wasn't your horse."
"Oh dear," the Doctor's face fell. "You see, I didn't really mean any head. I meant ahead."
He glanced hopefully at Jamie, who looked confused.
"How to explain...," he mused.
"Oh, when the malt tax collectors came, you were ready. You were ahead."
"No," Jamie frowned. "I was a wee child of one."
"Oh dear."
This would take a whole day.