Mycroft looks around for somewhere suitable to sit, but there aren't many options. He decides to go for a plain-looking stool that, despite its inoffensive looks, has surely seen its share of sin. Ah, yes, from this angle he can see tooth marks in the wood. Delightful.

"I wasn't the one who scheduled this meeting, Ms Adler," he says, crossing his legs and smoothing his suit (it's difficult to look dignified while sitting on a stool, but difficulty never stopped Mycroft). "Nor was I the one who wasted both our time with those ridiculous carriages, though I'm sure the amusement must have been worth it to you."

His tone is unaffected, his expression 'vaguely interested.' He's not concerned about Irene's time or money. Neither is Irene. They'll both do things exactly the way they want them done, regardless of their surroundings. Mycroft knows that if this job were to get in Irene's way, she'd toss it aside without hesitation.