Christoph was just putting his drink to his lips again when Jachen whispered in his ear. The surprise was enough to make him jump and consequently to choke on his drink. In the midst of his coughing, he managed a faint, "Mein Gott!" Finally managing to clear his throat, he turned and clapped Jachen on the shoulder.
"Jachen!" he exclaimed, completely ignoring the other man's whispered comment. "So good to see you again... but really, did you absolutely need to sneak up on me like that?" He cleared his throat again to emphasize his point.