MPs will spend a total of 12 hours debating and voting on 14 Lords amendments to the EU Withdrawal Bill - six hours on Tuesday and six hours on Wednesday.
Dominic Grieve and his fellow would-be rebels were called in, just moments before the key votes, and offered personal reassurances by the prime minister over what happens next if MPs reject the government's Brexit deal.
Theresa May ultimately persuaded all but two of her MPs to back her in the decisive vote in Westminster on Tuesday - but she increasingly appears little more than a hostage to the warring factions in a bitterly divided Conservative party.
Now the focus shifts to the price of the rebels' compliance, and it could be a high one for the beleaguered prime minister.
The government says the changes would weaken Britain's negotiating position and is seeking to reverse them in the Commons.
The BBC's political editor Laura Kuenssberg said she had been told by a government source that no actual concessions had been agreed and the only agreement was to keep talking.
Tuesday's Commons debate marked the start of the government's attempts to undo most of the changes to its EU Withdrawal Bill that were put forward by the House of Lords. MPs would then be permitted to vote on the final Brexit deal, igniting fear in Brexiteer MPs, as parliament could also halt the Brexit process entirely.
In a day of drama, May's position seemed suddenly weaker when junior justice minister Phillip Lee, who has always been critical of Brexit strategy, resigned and said he would vote against the government.
With the Conservatives having a majority of just 13 thanks to the support of the DUP, it would only take a handful of Tories to side with Labour and defeat the Government. The views expressed therein are not necessarily those of stlucianewsonline.com, its sponsors or advertisers.
Brexit Secretary David Davis, who reportedly has clashed with May, has warned Conservative Party rebels that proposals to give Parliament the power to direct negotiations with the European Union are simply a tactic to overturn the results of the 2016 referendum that mandated Britain's departure from the bloc.
As with last week's set-to with Davis over the Northern Irish backstop, both sides of the Brexit culture war in the Tory party were nearly immediately in dispute about what the climbdown meant - and who had won.
Her concession to discuss the changes may mean lawmakers could have more power if she fails to secure a Brexit deal, possibly leading to a softer approach to Britain's divorce.
The legislation is now back before the House of Commons after a total of 15 defeats by the House of Lords.
As time ticks by, May can no longer kick decisions down the road, increasingly under pressure from European Union negotiators to come up with detailed positions not only on customs, but also on future trade relations and governance.
Nicky Morgan has been an outspoken critic of Brexit, but she backed the government following its concessions.
At the very least, Grieve and his colleagues have succeeded in throwing up a series of new parliamentary barriers to a no-deal Brexit.
British Prime Minister Theresa May narrowly avoided a major blow to her Brexit strategy Tuesday after MPs rejected a plan that would have given parliament a veto on the final deal negotiated with Brussels.
In the event, Dr Lee abstained on the crucial vote, saying he was "delighted" the Government had agreed to introduce an amendment giving Parliament "the voice I always wanted it to have in the Brexit process".