Is it at all possible that sergeant Stephen whites story was true but it wasn't white but a different police officer who had the encounter and it was hushed up to avoid embarresment.This story could have been passed round the police forces and later on in his life white inserted himself into the story.
World opinion is divided on this matter: I tend to think there's truth in this, and the rest of the world thinks otherwise.
I think it is Castle Alley as it is the only place that can reasonably be described as 'just off the Whitechapel Road'. In terms of the cul-de-sac comment, almost, in fact near enough for me.
We do know from press reports that the two policeman regularly patrolled Castle Alley, so regular that the police passed through every 5 to 10 minutes. The reason given by the press was none other than it was supposedly the most dangerous street in the area. This would support White's claim that two policemen were posted there and were only gone 5 minutes.