Westminster Council have been digging up Maiden Lane for months now, and laying very expensive-looking granite setts. Below you can see the state it's been in:
On the plus side, there's not much traffic going down there yet, but that's because the taxis and van drivers haven't discovered that it's been re-opened yet.
So in summary, Westminster Council have taken a narrow, pedestrian- and cycling-hostile central London rat-run and transformed it into...a narrow, pedestrian- and cycling-hostile central London rat-run. And the cost of this? Well, I can only guess, but they've been working on it for some months so it could be well into 6 figures.