As Mycroft and Sherlock reach the car Mycroft stops and turns to face his younger brother with an outstretched hand. Sherlock sighs and rolls his eyes then places the pistol in his brothers hand.
"You like to take all excitement out of any situation dont you brother"
Sherlock tells Mycroft with a slight tone of amusement; knowing fully well that Mycroft never goes a day unguarded. All the cameras and security checks in all of London bow to his will. As well as probably the next 50 people withing a 100 yard radius of Mycroft. All working to protect him.
Mycroft slides into the front seat of the car and before Sherlock can follows suit into the back of the car, Mycroft calmly says while looking straight ahead, and no hesitation in his voice.
"We've lost John Watson. "