Dean Bradley, aka The Cobra, is an agent with British Intelligence.
[Note straight off that I have seen the first name printed in numerous places as "Dean" and in several places as "Deen".]
How this man came to be part of that organization in the years shortly after the end of the First World War is unknown but it must have been interesting because Bradley is a fellow born to American parents while they lived in India and who grew up in that huge country even after his parents were killed during a revolt against Westerners when he was still a youngster. He was in a way adopted by a wealthy yogi who taught him many things normally not passed to outsiders. When Bradley was old enough, he was sent to England to complete his education at a prestigious Oxford college.
After his schooling, Bradley returned to his beloved India where under his legal name he took a job with British Intelligence, although I read one place that he was affiliated with the "Bombay Department of Justice", and soon gained a reputation for getting the job done quickly and decisively. When he later moved his operations to England with a sojourn to the States, his expertise and experience were readily accepted. It is interesting that to many in India, Bradley is decidedly a Westerner, treated as British for the most part but occasionally even having his American nationality mentioned, as in his being a "Yankee dick".
Even as he was so employed, Bradley began his secondary career being a costumed crimefighter who went after those that had proven untouchable by legal means. As The Cobra, his manner of dealing with these criminals was swift and deadly and designed to strike fear into their hearts as they learned there was no legal appeal and means of avoidance. With the use of a cigarette holder, said to be "peculiar greenish", which he rigged to shoot small darts whose tips had been dipped in paralyzing lethal snake venom, his impressive aim brought a good number to targets to their end silently and frighteningly.
One might think that a vigilante who kills his targets without consideration of jurisdiction or authorization would be anathema to the police but apparently in the world of The Cobra, he is highly respected by those in authority who know of him; as one Scotland Yard inspector tells his boss, "I don't know who or what the Cobra is. But I do know that he gets results."
Bradley is described as "high-foreheaded, dark-skinned, he had black eyes (elsewhere referred to as 'cobra eyes') which glittered coldly like ebony diamonds, hard, unemotional. He had no mustache. His face was thin and sharp (said to be 'hawk-faced'). His lips, narrow and straight?lined." His strength is mentioned as being "astonishing".