Well that escalated quickly.
Scarcely had the ink dried on the litany of articles about the Eurosceptic subset forming in the Tory ranks when David Cameron unleashed his rebuttal, indicating that he would require any of his ministers who opted to go against the 'Yes' campaign to resign.
This, combined with his pro-EU chatter leaking from the G7 summit and the revelation that the government could spend exorbitant amounts of tax payer money on the 'Yes' campaign, is a body blow to those readying to lead the charge to extract Britain from the EU.
As David Davis succinctly summarised, Cameron risks "turning a decent debate into a bitter argument" - a bold move for a leader with a slim majority and an already restless backbench. So is this sheer hubris on the part of the PM, or does he have a battle plan ready to implement in the face of a party rebellion on Europe? Stay tuned...
UPDATE: Cameron is seemingly backtracking on Sunday's comments, saying they were misinterpreted - that remains to be seen, but at least the threat of a full fledged rebellion will subside for a while.