Sherlock was not a stranger to cocaine. He was not a stranger to most of the harder drugs out there, much to the disappointment of Mycroft, and he had really gone down a hole once or twice in his younger days. Not since meeting John, not since a short time before that when he had managed to get Lestrade to allow him to work on murder cases. Oh, he slipped every so often, but always carefully.

This was not careful, this was not a dose he had chosen for himself, and so he immediately put the cup down on the table.

"I like to allow you some smaller victories," he said, voice level and calm despite the inner deductions already racing at the likely solution percentage and how badly it would affect him. "It can demoralise an opponent if they are consistently crushed."