Arriving at the top floor, the 26th, The Doctor was almost deafened by the cacophonous sounds of thousands of chimes. Through the windows he could see the cloud of Cadullons, circling their meal. Eventually they would get tired of waiting, and descend on the whole of the city, gorging themselves until they could barely fly, devouring massive chunks from every building in London.

"Alright…roof access…roof access…where is the roof access? Why are these things never easy to find? It's like there's a genetic fear of roofs going around this planet…Ah! There it is"

The Doctor made a B-line to a door clearly marked "ROOF ACCESS. AUTHORIZED PERSONEL ONLY" pushed it open and hurried up of a small flight of stairs, opening the door at the top and walking out onto the top of the building.

"Now, Where were w-"

He was cut short by the sight of two figures in front of him, standing on the edge of the roof trying to lure a member of the flock towards them into a small cage they had between them. The sight of these people themselves wasn't nearly as jarring as what they were wearing. The one on the right, a woman, had on a large black coat decorated with various patches and matching black pants, her medium length brown hair held back in a ponytail. The figure to her left, a man, was wearing a cream coloured jacket and light brown plaid pants, with a panama hat with a garish hatband around it. He held out a green umbrella with familiar, red curving handle, which he was using to try to herd stray Cadullons into the cage. The figures were shouting to each other over the wall of noises produced by the circling flock, the man seemed to be giving instructions to the girl, who was entirely preoccupied with taunting the birds.

"Oi, bird brain! Get over here!"

"Come now Ace, don't taunt them, we just need to get one and get off this ghastly roof"

"Oh, fine" she sighs, stopping the taunts

"Um. Hello" The Doctor pipes in "What are you doing?"

The pair whip around to face the doctor. The woman quickly sizes him up, while the man simply looks at him with an inquisitive stare. After a brief moment of silence, the man speaks up

"We're ornithologists, trying to collect a specimen for study. I'm The Doctor, and this is Ace. May I ask your name, sir?"

"Um..ahh…John. John Smith, building inspector" The Doctor stammers "Those don't look like any birds I've ever seen" Why couldn't he remember this? Surely if he had met himself he would have made a note of it.

"Well they're not really" Ace chimes in "You see they're from another planet, and we've been sent to catch one by one of The Professor's friends. What was his name again?"

"Stewart. Brigadier Stewart. He's dealing with a certain… foreign dignitary, who has asked that one be brought to him"

"Another Planet?" The Doctor asks, with all of the false surprise he could muster "Like from outer space?"

"Exactly. You see, Ace and I here are travelers through space and time"

"Incredible" The Doctor said with considerably less surprise. How many times had he given this same explanation? At least five hundred, he guesses. Or five hundred and one, apparently.

"Could he see the TARDIS, Professor? Just a quick tour?"

"Nonsense. We must be off anyway" He quickly spins around, hooking a Cadullon with his umbrella and swinging it into the cage.

"Picked up that trick while studying Venusian Aikido as a young man" he says with a grin.

"Well now, let's be off. Come along, Ace" he grabs her by the arm and heads for the door

"What are you two gonna do about all these alien birds, then?"

"Oh don't worry mate, the Proffessor says that they'll all get frightened off in a few minutes, won't let us stick around to watch though, says he should get the TARDIS out of here before then"

"And why's that"

"Well I wouldn't expect a couple of humans such as yourselves to understand, but it's because there is about to be a level 12 temporal disturbance, which would play all sorts of havoc with my navigation systems, so we really must be off. You know what they say, 'a stitch in time says goodbye'" and with that, the Doctor and Ace, rolling her eyes, went inside, leaving The other Doctor on the roof

"Class 12 disturbance?" he said to himself "What's going to create a temporal event of that size in the middle of London?"

Then he had an idea. Originally he was going to use his sonic screwdriver to cause the tower's glass to vibrate at a frequency that the Cadullons would find painful, driving them off, but that interlude with himself had cost precious time. Then he had an idea. He turned and sprinted down the stairs.

…

Bursting out of the building front doors, he was just in time to see a portable loo disappearing before his eyes. At least, that's what he thought it was upon first glance, though now he realized that is must've been the TARDIS. He quickly made toward the alley where he had left his own, unlocked it, and stepped in.

"Right, just have to pull up flight records for this terrestrial date" He thought out loud

"Ah! There, they're off to UNIT headquarters, exactly 15 years, 7 months, 12 days, 3 hours, 8 minutes and… 5 seconds ago"

With that, he started turning knobs, adjusting dials, and flipping switches. Finally, he braced himself, and activated the engines.

Now, it just so happens, that when any two time-fairing crafts happen to run into each other while in transit, they let off a massive charge of chrono-energy, rating a 5 on the Grand Gallifreyan Temporal Disturbance Scale. When both of those craft happen to be the very same ship, separated by the expanse of time, the rating will jump up to a 10. When both of those craft also happen to be The Doctor's TARDIS, with a time war in between them, with one purposely aimed and fired at the other at a billion years an hour, the rating will reach approximately a 12.

The two ship crashed together, causing a disturbance in time so powerful, that Aristotle was able to have a brief conversation with King Henry VIII. The younger doctor and his travelling companion were, of course taken completely of guard, as the TARDIS fused with itself, the Time Rotors moving as one. When the shock had subsided, The Doctor and Ace suddenly found that they had taken on another traveling companion, and the TARDIS had adopted and new interior.

"Who in the name of Gallifrey are you?" The Doctor demanded of the intruder

"Well… I'm definitely not a building instructor"

"Listen mister" Ace interrupts "answer his question or will tie you up and toss you out into space"

"Alright! Alright! Calm down! The thing is…" he says, turning to his younger self with an older face. "I'm you. Well, sort of. You become me"

"I see. Well, hello Doctor"