It started after Trenzalore. The walls they had so carefully erected and enjoyed dancing around for months had now crumbled to the ground, and in their absence had grown a closer relationship than either of them had experienced before. Yet it felt good; it felt natural.
The two participants in this newfound closeness are currently curled up on Clara's bed, facing each other, and talking. After Trenzalore, Clara had decided that she wasn't ready to go back to the Maitlands, and the Doctor had decided that they sure as hell weren't ready to travel the universe looking for adventure, so this is how they spend their days now: talking, while the TARDIS lingers in the vortex or drifts in empty space. They talked about all the past lifetimes where they had unknowingly encountered one another, shared stories and filled in the gaps in each other's memory. Clara's memories were like memories from a dream; difficult to remember, but always there if you knew what to look for. Not all that different to the Doctor's memories from past regenerations, really. And so they helped each other rediscover the past, talking into the night every day.
This particular evening, as the long hours of the evening grows into the small hours of the night, their conversation becomes quieter and, as most conversations occurring when the lights are dimmed and the rest of the world is only notable for its absence, turns more personal. Feelings one would be afraid to admit to in the light of day, such as fear and loneliness, are slowly owed up to and shared, and perhaps mirrored in each other. It could be hypothesized that conversations such as these are the only foundation upon which one may build a true friendship. The only time we can truly know ourselves, and therefore the only time we can show ourselves to others. For these two individuals in particular, though, this is the first time they have had such an opportunity without the vast vistas of secrets and doubt separating them. Where he before had been afraid to trust, he now wishes to share himself, and divulge for her his past. Where she before had wanted to impress, she now wants to let him see her for what she is: herself. And so they talk.
The clocks don't tick in the vortex, but we eventually find our two intrepid travellers asleep on the exact bed where they have spent their evening. She has turned on to her other side, facing the wall. He has fallen asleep still wearing his suit. About halfway through what would anywhere else be considered a good night's sleep, he wakes with a start, bolting upright and instinctively reaching out for his companion. She remains fast asleep; otherwise she might have mentioned how the way in which the cradles her head and plants a quick kiss on her brow might be interpreted as slightly more than just platonic. Or she might not have. We don't know. He smiles down at her peaceful features for a long moment, before sliding out of bed and tiptoeing to towards the door. His careful movements can't have been as soundless as he had hoped though, or perhaps she wasn't as deep asleep as we have been led to believe, because before he can make it to the exit, her sleepy voice pipes up: 'Doctor? What are you doing?'. There is no call for dishonesty, and the idea of lying to her doesn't even occur to him. 'I didn't mean to wake you. I was heading towards the hallway, to go to sleep in my own room'. She is still facing the wall, away from him. 'Oh', she replies, and then 'Why?'. It's a fair question, and in her sleepy state she asks it without implications of any kind, simply from curiosity. He mulls this over in his mind for a while, before realising (to his own great surprise) that he hasn't got a good answer for her. A soft smile graces his face as he takes in her form lying there, probably already gone back to sleep. 'Why indeed', he mutters to himself before removing his suit jacket and vest and shoes, tiptoeing back to the bed, and tucking them both in under the sheets. He is facing her back now, and an impulse has just struck him. An impulse he fears is rushed, risky, ever so slightly dangerous and, one could even say, borderline inappropriate; they have yet to establish where the borders of friendships will be drawn (or even on which side of this line they would like to find themselves), and he fears this impulse might be overstepping it. Yet he cannot deny it, and ever so hesitantly he raises his hand to place it where the curve from her hip meets her waist. He is suddenly so nervous about this entire endeavour that when she reaches up to take his hand, he jumps away, an apology already on his lips. But she doesn't swat him away, like he thought she would; instead the takes his hand in hers and pulls it over her waist and to her front, her back now fully against his torso. His sigh of relief matches her sigh of comfort. He is even to far wrapped up in his sudden rush of happiness and affection that he misses the loving smile which appears on her face and which doesn't go away even as sleep seizes them both.