Take a risk, take a chance, make a change... And Breakaway...
The Doctor stared at the girl who'd just announced she was taking over. "I'm sorry, what?"
Reyanne McCall was standing belligerently with her hands on her hips, like a small child. "Just what I said," she replied.
"Right..." the Doctor answered. "And I'm going to allow that because...?"
Reyanne chuckled, setting down her bag and sitting cross-legged on his chair. "You need a guide, Doc. You've never met Wellington, and how will you react when you do?"
His eyebrows furrowed, and he blinked at her, clearly not comprehending in the slightest. Reyanne rolled her eyes. "The Duke of Wellington? Lord Arthur Wellesley?"
"Right... So I'm going back to the Napoleonic War?"
"I knew you'd get it!" she crowed, clapping at him.
He pulled her hands apart an knelt in front of her, saying, "Give me a good reason why, and I may consider it."
She took one of her hands away from his and placed it on his cheek. When he didn't pull away, she smiled and said, "Because you need to meet me, Doc. My name's Reyanne McCall. I'm, depending what time we're in, a two-hundred-and-twelve-year-old Napoleonic soldier's wife. I know everything about you, but you know nothing about me. So you need to meet me."
He stood slowly, raising himself to his full height and looking down at her menacingly. Strangely enough, she laughed.
"Whatever, Doc. First, you need to go back to 1802. That's when I first met you. I was seven. You'll arrive in Rochester, just outside the Castle, to be exact.
"Then you'll go to 1808, my wedding day. Just by my being here, the Tardis knows exactly where to go.
"And the last place and date is a surprise. I can't make things too easy for you, now, can I?"
As she'd talked, he'd been shaking his head. "Why now?" he asked.
"You gave me a letter, telling me all of this, and no, you can't read it. Timelines, Doc!"
He nodded. "OK then."
She jumped up, saying, "Wonderful!" she picked up her bag. "Right. As soon as I leave, the Tardis will start going. So sit down and enjoy the ride, Doc. Once you land, obviously, you need to leave. The Tardis won't go again until you've seen and done what you need to."
Kissing his cheek and waving over her shoulder, she said, "Have fun, Doctor!"
As soon as she'd shut the door behind her, the Tardis started to go, and she stood back with her hair blowing in the wind of the Tardis' leaving.
Grinning, she winked out of sight like a bursting bubble.