John pulled the coat around himself tighter and tried to keep from closing his eyes and burying his nose into the soft wool. It smelled like cigarettes and crisp air and Sherlock. It was ostentatiously long, especially for John, swinging about his ankles. They were only a few blocks from Baker street; there had been a grand opening for a new diner nearby and it had only taken two hours of negotiation (and one call to Mycroft) to convince Sherlock to come.
By the time they made their exit the air had gone still and frosty. John tried not to be bothered by the cold, but Sherlock noticed (Sherlock always noticed) John's discomfort and handed him the coat wordlessly. It was too chilly for him to even think about rejecting.
They walked silently for a while, until John was feeling warm enough to speak. Then he mimicked Sherlock, popping the collar and putting on his best brooding look, along with a ridiculously deep voice.
"Look at me I'm Sherlock Holmes! Time to go to my mind palace!" His face contorted into a look of intense concentration. Then it was gone and he snickered.
"Oh, give me my coat!" Sherlock's voice signaled annoyance, but there was no mistaking the half smile on his face.
"Never!" John said, skipping ahead. He had abandoned the Sherlock gag in favor of giggling and twirling around in the long coat, hopping out of reach everytime Sherlock reached for him.
"Honestly, John."
"Honestly what?" John smiled wickedly. "Can't catch a man with a limp?" And then he was off, racing down the block with the coat billowing behind him as he ran, like a cape.
Sherlock sighed, smiling widely to himself before taking off after his companion. Oh, the chase was on.