Over the years, the Doctor had travelled with scores of people, nearly all of them from shorter-lived species than his own. In his first journeys with humans, he realised that if they had any hope of adjusting to the tedium of life on one planet, in one time, they couldn't stay long with him. So he decided a subjective time of two years should be the absolute maximum. And that was easy to enforce.

The Doctor also had a definite policy when it came to his degree of involvement with his female companions.

No romantic relationships.

No sex.

No "fooling around."

This policy was rooted in how short-lived humans were: He would just be settling into the relationship when a human partner died. Maybe when he neared the end of his thirteenth regeneration he would reconsider, but until then ...

After the Great Time War, when there was nobody of his own species left, he only became more resolved to hold aloof. He had destroyed his entire world, his race, his civilisation, billions of years of knowledge and art, to preserve these little, primitive people and untold numbers of others like them – and they were singularly unaware, ungrateful, uncaring. He tried to remember they were relative innocents, children in the universe, but sometimes he couldn't keep his anger in check. But after he snapped and called his human friends stupid apes or otherwise rubbed their noses in his supposed superiority, he felt awkward and ashamed. They were not his equals in most ways – except many were better than him in terms of courage and compassion, especially the way he was now, when he struggled to build a shell around his wounds without closing himself off to all emotions, struggled to keep from becoming hard and bitter. And there were the terrible nightmares, the unpredictable eidetic memories that plunged him into the war all over again ... he couldn't inflict that upon anyone in good conscience. And he was sure that he couldn't take losing someone he allowed himself to love, ever. One more loss was too much to think about.

The trouble was that inviting a woman to come travel with him implied a romantic interest, no matter how the invitation was issued. Picking someone out of a crowd of billions was flattering, even if it was done more or less randomly; taking her places no human male could take her – it had "courtship" written all over it from their cultural standpoint. Those women who did find themselves attracted to him – and there were enough for him to realize there was a pattern – couldn't help but hope that maybe something was going to change. He thought maybe he should just travel alone, but he needed company, a distraction, to focus him on the here and now.

As far as the ambiguity of the situation went, he'd concluded that the best, kindest way to handle the situation was simply to continue to be a friend/mentor and not take the slightest bit of notice of her signals that more would be welcome.

Sometimes, though, those signals were hard to ignore, and the very reasons he cited to himself for avoiding involvement became reasons for him to get involved.

He was momentarily trapped in a hospital in World War II London, ca. 1942, with Rose Tyler, a child, even by human standards – nineteen, maybe 20 -- who was watching as he tried to resonate concrete with his sonic screwdriver, setting up a vibration so the bars across the windows would loosen up and come out and they could escape. Supposedly Jack Harkness was coming to rescue him and Rose, but he didn't trust Jack as far as he could throw him.

His mind was multitasking: part paying attention to the concrete; part listening to Rose chattering away about how wonderful Jack was; part thinking about another time he had resonated concrete with a prototype sonic screwdriver while a woman – his eventual wife from his long-ago first lifetime – teased him about his studious, technological bent. They were still in the Academy; he was a mere stripling, not even 70 yet, and she was a few years younger; and this was supposedly a date -- but the idea for the sonic screwdriver had come to him about an hour before he was supposed to take her out; so instead of going to the Grand Prom, the two of them sat in his dorm while he assembled the thing, then tested it. She finally lured him away from his testing by playing some dance tunes on the sound system and challenging him to prove he didn't have two left feet. They danced around the room through two full repetitions of the recording. Their dancing started formal, soon turned into little more than rotating hugging, and ended with a kiss that made him realize he had fallen in love with her.

His wife had died long ago, and he had laid her to rest in his heart; but the parallel between those early days and now was making him nostalgic. He imagined dancing with her to this song – so different from Gallifreyan dance music, but reaching the same places in the heart and soul ...

"I trust him," Rose said of Jack, "because he reminds me of you ... except with dating and dancing."

He shook his head, annoyed. When would she stop assuming things based on her stupid superficial limited human perceptions?

"What?" she asked.

"You just assume –" he muttered.

"What?"

"You just assume," he said, a bit louder, "that I don't dance. Nine hundred years old, been around a bit, you could assume that at some point I did in fact dance."

They continued in this vein for a few minutes, until the Doctor said, "Well, I've got the moves, but I wouldn't want to boast."

Rose got up, cranked up the old Victrola radio as loud as it would go, held out her hand and said "You got the moves? Show me your moves."

Without thinking about it, he snapped off his sonic, jumped down from the ledge where he was standing, and walked toward her. He laid his hand in hers and her touch was electric. The warmth of her body against his, the scent of her hair, the way she hid her face in his shoulder and held him tightly at the waist – it was all soothing and upsetting at the same time. Soothing for obvious reasons; upsetting because it continued to remind him of the only woman he had really loved ...

Now would be a good time for you to come back, Jack.

But Jack didn't appear, and Rose ran her hand up his back in a comforting caress. He bent his head over hers, resting his cheek against her hair and holding her tightly. He had never thought about it before, but now he realized his wife's early death was far more preferable than the deaths his fellow Time Lords had experienced ... and would he have found the courage to kill her as well as the rest of Gallifrey?

He swallowed against the lump in his throat and squeezed his eyes shut, hoping Rose wouldn't notice. She had a tendency not to notice things that weren't right in her face ...

But she nestled closer and stroked his back comfortingly, and he could feel the unasked question in her hands. He tried to choke back his grief, but it burst out of his hearts, screamed up his lungs and out of his mouth, burned his eyes, clubbed him behind the knees and bashed him over the head.

"Doctor? Doctor! What is it? What is it?" Rose was screeching, but he couldn't answer her; Gallifrey was burning again, shaking, erupting, exploding; the death screams of his fellow Time Lords and other Gallifreyans shearing through his brain as they experienced rapid regenerations, the next starting before the previous was even complete ...

He couldn't speak, and he knew it might overwhelm her, but he had to explain or just share with someone – he took her head in his hands and pressed his forehead to hers, just for a few seconds. She jerked away with a sound that wasn't quite a scream, but more than a shriek, and crouched just out of his reach, trembling.

But then she pulled him close and re-initiated the contact herself. He tried to edit the worst of it, but even so her horror was palpable. Then as she took in the fact that he himself had turned Gallifrey into an asteroid belt to save the rest of the universe, her fear and terror turned to gratitude, and she kissed him gently on the lips.

He wasn't sure how long it had been since he had last been kissed this way, apart from too long, and that since it had happened there was no reason to stop. He pulled her gently down to the floor next to him without breaking the kiss, and she pressed tightly against him, twining her leg around his. He wept again, but this time with joy; for the first time since the war, he was able to stop thinking about it ...

They left World War II behind. Just this once, everybody lived. He was euphoric, walking on air; this was the best day he'd had for at least 700 years.

As the TARDIS sped through the Vortex, they killed a half-bottle of champagne that Madame Clicquot had given him herself in the early 1800s, with instructions to save for a special lady. It had waited in stasis all this time, and tasted as fresh and bubbly as anyone could want. He sat next to Rose, holding her hand, kissing her, making her laugh. But soon he realised she was holding back. Maybe she thought it was the champagne talking. He did feel a little giddier than usual, but that was at least as much from the events of the past few days as the bubbly. He decided he needed to make himself, his feelings, clear to her.

He hesitated a moment. Rose always said the right things – "No, of course we're not involved!" -- but at times she seemed to want to be. She always stood closer to him than she needed to ... didn't she? She had initiated the dancing ... hadn't she? She had been using Jack to make him jealous ... hadn't she?

He let a silence fall, then cleared his throat.

"Rose ..." he began, looking at the empty half-bottle. His voice sounded harsher than he intended.

"I know what you're going to say, Doctor," she said tonelessly, also staring at the bottle. "I agree."

"You ... " Was it really going to be this simple? He felt a big, stupid smile spreading across his face and turned to her, but she was now looking at something in a far corner.

"It was nice, don't get me wrong ... but well, there is that huge age gap. And ... I'm too 'human' for you, aren't I? An 'ape.' "

"Oh." The smile vanished. He bit the inside of his cheek. He had said those things ... many times. "It's just frustration, I don't mean it ..."

"Really."

It was the first time she'd ever let on that she was offended. She said nothing else, and he left, quietly, his eyes stinging.