My vote is for12 Dec 2019 18:48
Vanadium - because
it's the only battery technology that is strong and stable enough to get FossilExit done,
will last at least 4 terms of the fixed parliaments act,
can take from the energy-rich and feed the energy-needy,
is not controlled by Russian agents,
won't burn like the Australian outback,
and like some politicians we know, can discharge multiple times a day without loss of capacity.