It's his dry sense of humour that prompts him to choose a Friday night. Fish and chips will add a touch of informality to the meeting; he knows that most people find food reassuring, particularly when it comes to comfort food.
He's aiming to put John at ease for once, wouldn't want him to get the wrong idea on this specific occasion. The delicacy of the situation requires the utmost diplomacy; there is too much at stake, he can't risk angering the good doctor into doing something both of them might bitterly regret later on.
"I'm delighted that you decided to come, John," he greets him, using the suave tone he specially reserves for talking people around.
"I don't expect I really had a choice."
A smirk touches his lips, and then it's gone. "Have a seat, please. There are some matters I would like to discuss over dinner, if you don't mind."
John pauses as the valet brings in the plates. "Is that fish and chips?"
"I should think so, yes."
"So we're actually going to have fish and chips for dinner."
"Brilliant deduction, Dr Watson," he says wryly, patiently waiting for the man to elaborate on his previous remark.
"I mean, I thought you didn't do fish and chips. It's so –"
"Ordinary, you mean?" he offers, and gestures for him to sit down. "Ordinary is fine. Sometimes."
He watches as John takes place in front of him, nibbles a chip as if to prove he's not trying to poison him. "This is delicious. Try it."
John only stares at him – he can see his mind racing in the attempt to work out the reasons for this ersatz business dinner.
"It's about Moriarty, isn't it? He's back, and you're worried about Sherlock."
He tilts his head to one side, pretending to consider the idea. "You're getting better, John. However, I regret to inform you that things aren't always as they seem."
"Meaning?"
He shrugs noncommittally. "I wouldn't be overly concerned about the matter if I were in your shoes. The news of Moriarty's return might have been a little – exaggerated, if you understand what I mean."
John's eyes widen in surprise as revelation finally hits him. "Oh," that's all he says, and Mycroft offers him another of his well calculated smiles.
"I knew you'd eventually get there. Needless to say, you shall not share this information with anyone else."
"Or what?"
"You don't really want to know," he states pleasantly, though he's well aware it's just a bluff on John's part. Sherlock is back, and that's the only thing that truly matters to the both of them.
The doctor shakes his head as he finally tries the fish. "You're right, this is quite good."
And you're not the terrible brother you pretend to be, his body language all but screams.
Mycroft studiously ignores the evidence, turns his undivided attention to the plate resting before him instead. They spend the rest of the meal in something close enough to comfortable silence, and John wishes him goodnight before he leaves.