Ooops I made a big mistake.
It's NOT a standard micro USB charger.
The charger has a standard USB connector but the socket on the camera is NOT a micro usb one.
It is a non-standard camera specific lead.
This is crazy, how stupid of Nikon.
To charge the camera or to take photos of it you have to use this non-standard lead.
Whilst all phones are now standardising on micro usb, Nikon make you carry round an additional lead.