Luther's normally not the best at reading people, but he does know the sound of an actual, proper fan. He's spent enough years back home and now in the City to recognise it; it was their bread-and-butter for a while, after all, the bright eyes and hitched breath and enthusiasm to see a real live superhero in the flesh. The excitement, even when it's bitten down and hidden.

This woman does not have it. Her sarcasm is withering.

And for a second, it actually reminds him of Diego's acerbic humour. And so instead of just smiling that bland, bland smile and letting her get on her way — no need for him to needle the bystanders — instead of all that, Luther actually takes a moment to flash a glint of dry humour back. "You sure you don't want my autograph?"

He hasn't recognised Georgia yet, but he's recognised her lack of enthusiasm — and rather than be offended, he's just bemused.