Positive grounds! What can ya' expect from the goofy (er, excuse me - the eccentric) Brits.
Fortunately, they quit doing that decades ago.
But they still drive on the wrong side of the road.
Some MGs had two 6 volt batteries in series to make 12 volt, both mounted under a hatch right behind the driver and passenger.
What me worry?
Another version of the MG had the electric fuel pump wired in series with the tail lights. If the light bulb blew, the pump quit.
Some people think MG means Morris' Garage, but it really mean MiGraine (as in headache).
But their beer is good.