The Whitechapel series isn't merely an excuse to use copy-cat crime ad nauseam. That's fun, but it would quickly lose its realism, if that was the case. Not to mention the fact that it would be very bad luck for the borough involved!
When the second series was announced, I think most people groaned a little. The first had been so good, that repeating it could only dilute the concept. No area would attract so many psychotic historians. The fact that they had one was incredible enough.
Ben Court and Christine Ip didn't do that to their viewers. Every story has a different twist and another way to utilize the lessons of the past, in the investigations of the present.
Jack the Ripper wasn't Whitechapel's only world-famous criminal. During the swinging Sixties, the Kray Twins reigned supreme from neighboring Bethnal Green. But their street ran straight through the border and some of their crimes were committed in those pubs.
Styled after the Mafia, Ronnie and Reggie Kray were eventually caught and locked away. They both died behind bars, after each spending over thirty years there. Hence it's a little perturbing for Chandler et al to discover that another set of Kray twins are terrifying local residents into silence.
There are no hidden dimensions here. Jimmy and Johnny are quite open about their gangster activities, safe in the knowledge that nothing will stick long enough to warrant their arrest. But Buchan has access to the original Kray police files. Will he find mistakes in history, that can be prised open now?