The government threw everything at trying to defeat Tory rebels led by the former attorney general Dominic Grieve and their amendment to the EU (Withdrawal) Bill - which forces the government to enact a statute "approving the final terms" of Brexit before the UK leaves the EU.
And that is one of the big reasons why this defeat for Theresa May matters: it shows the fury among some of its MPs, notably those who voted to Remain, that they are being ignored, as Theresa May engages in the most important negotiations relating to this nations' future since those that took us into the EU (or what was the Common Market).
The point is that the rebels rejected a written statement first thing this morning by the Brexit Secretary David Davis, in which he promised a vote on the final deal by MPs and Lords "in the form of a resolution", as not giving them comfort that they would have sufficient time and latitude to really assess and judge the Brexit deal.
And literally minutes before 7pm, the justice minister Dominic Raab tried to offer another olive branch - which is that the government would reform its own bill in the next phase of its passage through the Commons to address at least one of the rebels concerns, namely that the PM and ministers would use their executive powers to sideline parliament and push through Brexit-related law changes by so-called Statutory Instrument.
Raab pledged these powers would not be employed till after Parliament had its say on the withdrawal terms. But in a rare and delicious moment of high drama, Grieve told Raab the offer had been made "too late"!
This is not a disaster for May - though it is an embarrassment that her authority has been undermined on the eve of the historic summit in Brussels which will approve phase one of our Brexit deal. But for the avoidance of doubt, none of the rebels say they want to stop Brexit. They just want more scrutiny of it, more influence over its nature.
This is cumbersome for May, because it may limit her flexibility in Brexit talks and their translation into British law. That is the annoying thing about parliamentary democracies. They don't allow leaders to do precisely what they want.
Robert Peston is political editor of ITV News. This was first published on his Facebook page.