What really gets me about this scene, is John’s tortured look after Moriarty asks Sherlock whether he thinks the consulting-criminal-thing is brilliant.
He’s checking Sherlock’s face.
“Brilliant” is what John tells Sherlock after his deductions, it’s how John feels about him. And he’s afraid that Sherlock thinks he’s stupid in return. That he’ll call Moriarty brilliant and amazing and everything John secretly wants to hear Sherlock tell HIM. John, with a bomb strapped to his heart, looks up to check if Sherlock thinks Moriarty is brilliant. And Martin Freeman really sells that emotion.