No sooner had Gordon Brown scraped through yesterday's Parliamentary vote on the detention of terror suspects than he faced what could be an even more significant test.
The prime minister is the only one of Europe's leaders able to stop the juggernaut that is the EU's biofuels policy but it is far from certain that he will do what ethics and common sense dictate that he should.
Brussels is determined to increase sales of biofuels in Europe aiming for 10% of transport fuel to come from biofuels by 2020. If this target becomes law, forests and grasslands will be destroyed at an unprecedented rate, rare wildlife will face extinction and the world’s greenhouse gas emissions will soar.
In yesterday's Guardian, the RSPB’s Ruth Davis wrote that the chances of biofuels cutting emissions largely depended on Mr Brown's intervention
There have been hints that Mr Brown, his Chancellor Alistair Darling and other government ministers now realise that biofuels are not, currently, up to the job of cutting carbon emissions. Most people now also accept that biofuel manufacture is responsible for 30% of recent food price rises.
There will be beneficiaries if the 10% target is bulldozed through - the corn farmers of the US already high on Washington's subsidies, the mighty ethanol corps of Brazil and farmers elsewhere seeking the green gold from what was once set-aside land.
But millions more will suffer and while the harm of biofuels is greater than the good, there is no point in producing them.
Mr Brown has faced a succession of stern tests in his short time in charge and none will be tougher than this. He can prove his mettle and his morals if he steps in this week to halt the biofuels express.
Read Ruth Davis's article here