By Steve Dinneen When was the last time you were laid out naked in an enclosed space, whipped with hot leaves and then dropped into a tub of freezing water? This may sound like a way of eliciting information from a detainee in breach of the Geneva Convention but it is in fact the most enlivening experience I’ve had in London (before midnight, at any rate). I discovered Banya No.1 almost a decade ago and have been an enthusiastic regular ever since, forever craving the next opportunity to emerge from the icy water feeling born anew, as if dunked by a secular John the Baptist, had he worked on t…