They say (apropos of this discussion) "Carbon Brief also attributes the precipitous drop in emissions from coal to the country's carbon tax, which doubled in 2015 to £18 ($22) per metric ton of CO2" (so perhaps we can credit the government to some extent :-). Of course, $22 per ton (per C? Per CO2? I can never remember) isn't large by ~$50 type standards which are what I tend to think of as "about the right value". But if that's big enough to have the "desired" effect, then fair enough.
* WATTS SIDEKICK COPS A PLEA ON THE 2nd LAW OF THERMODYNAMICS - RS