Berlin becomes first German city to make rent cap a reality | World news | The Guardian
http://www.theguardian.com/world/2015/j ... in-germany

It's a serious issue but that article goes Private Eye piss-take in places.

Mr. A said that his flat in Mayfair is expensive, when he shared a flat in Brixton with 4 other people ten years ago, he could pay for his rent by working one shift...

Most areas already have an unofficial M² price for rents. But there are no guarantees that that cannot rise steeply. This is a good move.

So, everyone starts charging exactly 10% above the stated local average and then that soon becomes the local average, rinse and repeat ad nauseam.

Not quite, they can't up existing rents mid-term. So they can only go up 10% at the end of the term.