It's not the first time he's been a woman- after the first few dozen lifetimes Merlin stop caring which body he woke up in, and he rather likes this one. He's not married to the identity- never really has been, but when the Cold War heats up and Arthur is nowhere to be found, Merlin says, fuck it. She joins MI-5. Is 00 before any other woman before, and picks the code name "M". Identity means so little here, but it's nice, to keep a piece of the past.
She marries Lancelot- now a simple stock broker. Has three children. Waits for Arthur.
Bloody bastard. He shows up with the Cold War is over.
Arthur's not going to be anyone's once and future king: not in the state he's in. Raised by Uther, after Uther killed his real parents, Arthur's attitude problem is more of an attitude crisis. He's been thrust into posh schools, stuck into posh clothes- his accent is nicely upper-class, but his eyes scream bloody murder.
Uther dies when Arthur is sixteen. M smiles quietly to herself and slips in. She keeps him in his silly posh school, but then puts a gun in his hand to see just what he can do with it. What his name was before it was James Bond doesn't matter; not really.
The last James Bond was smooth, debonaire, and his violence was always a bit of a surprise. He always seemed to be able to take it all off; washed the murder off his hands.
With this new James Bond the smooth, debonaire charm is always the surprise: the violence never is. He wears the blood of the dead deep in his own; he simply is James Bond- there is no desire to take it off or walk away.
The Prime Minister raises some concerns. M brushes them off- bloody politicians. She knows just what she's doing.
And then Morgana surfaces shortly after his promotion to 00 status, and M thinks she might be about to lose Bond to her. Vesper Lynd is a very compelling woman, and Bond almost throws it all away for love.
But Vesper has an agenda of her own, and although she loves Bond, she chucks it all away. It's a terrible thing, and M waits for him to return to her because he will.
Bond comes back with relaxed shoulders and a gun loose in his fingers, standing in front of her as she drinks sherry in her dressing gown. He has no sense of boundaries, to be in her house like this, but then she's never enforced them, not really. She's playing a dangerous game- betting the house, as it were, on a man who's frankly a bit of a sociopath.
She lets him bend to his knees, hands pushing her nightgown up her thighs. She puts a hand on his head as his tongue does clever things between her legs, lets her head rest against the back of her chair as he coaxes an orgasm out of her. He lifts his head, lips shining and eyes impossibly blue and- Merlin has never begrudged Arthur anything. He won't start now.
Bond is not a gentle lover. His fingers bite, and he's selfish when he doesn't think he has to be gentle. She bites at him, yanks his hair.
It's good fun, and every time he comes back to her it cements him as her man.
Not the government's, not MI-5's. Hers.
Some days, when she watches him coolly cut a man down, she thinks back to Arthur- to how appalled he would be. How he had been so tempered by responsibility, incapable of being this person.
She supposes that a millennia and a half will turn anyone.
Arthur saves the world a hundred times over, leaving a roiling ocean of blood in his wake, living according to his own moral code and tempered only by Merlin being the one constant in his life. Merlin points the gun, and Arthur pulls the trigger, and they change the world doing it; (save it, damn it- it doesn't matter, not after a while).
Merlin thinks next time, they will be better than this.
The blessing is that Arthur never remembers.