In Baltimore, and pretty much every American city, the mayor wields incredible power when it comes to policing. Most new mayors want their own person at the top, and they have priorities and initiatives that they would like to see carried out. Things can get ugly: Almost every Baltimore police commissioner in recent years has not been able to leave on their own terms, sacked amid bad publicity, soaring crime, or friction with City Hall.

In London, the commissioner of the Metropolitan Police Department has always been appointed by the national government, and its oversight and budget were set by an independent authority. The Mayor of London, though the city's top public official, had basically no official say.

Not so anymore. New mayor Boris Johnson last year placed himself as the chairman of the Metropolitan Police Authority and has been issuing directives, a shakeup that made waves here - and which City Hall said is finally holding the Met accountable to the people. One of Johnson's first acts as the head of the authority was to chase out the then-police commissioner, Sir Ian Blair, a move that was impossible as mayor but done through his position on the authority.

"From our point of view, the mayor is the overwhelming voice of the customer, and they've been asking for certain things for a long time, and we want the police to focus on those things," Deputy Mayor Kit Malthouse told me.

He said the national government, referred to here as the Home Office, had been focused mainly on the Met's counterterrorism efforts, letting day-to-day street crime lag behind as a priority. While Johnson still has no formal powers as mayor to control the police department, as chair of the police authority he's tasked police with focusing on issues ranging from gangs and knives to crime mapping and dog fighting.

"Londoners respond to it - to knowing somebody cares and is responsible for crime," Malthouse said. "Our postbag on crime went from 30 or 40 letters to 400 a week, just because finally, there's somebody who's responsible and will take political responsibility for [police] performance."

From my perspective, not fully knowing the political controversy this move caused, I think its refreshing that Johnson wants to "take political responsibility" for crime, because he's not only afforded himself the opportunity to take credit when things go right but to be left holding the bag when things go wrong. Of course, such an active role can also become meddling, and disruptive. Either way, this is a turning point of sorts in the history of the Met, for better or for worse.