The jangling nerves of Brexiteer MPs – chronicled by Paul in two key pieces earlier this week – have been given another tweak by the latest back and forth over the Withdrawal Bill.

Yesterday, the ever-well-informed James Forsyth reported that the Chief Whip had told the Parliamentary Conservative Party that the Bill would return to the Commons in what Forsyth described as ‘early to mid-June’. This morning, Andrea Leadsom would only tell the Commons that she was “very clear” that “I aim to bring back the very important Brexit legislation within weeks”, which meant “soon after the short Whitsun recess” – ie, not very clear at all.

The general assumption within Government is that this means the week commencing 11th June, not least because the EU Council meets on the 28th and 29th June, and there is no desire to arrive at that meeting with any impression that Brexit is at risk of cancellation.

It’s a measure of the tense mood on the Tory benches that there is some concern and debate about whether Leadsom’s statement constitutes a delay when compared to the Chief Whip’s reported comments yesterday. Would the week commencing the 11th be the same as ‘early to mid-June’ or not? If not, would that mean the Bill’s timetable is slipping on a daily basis?

It might sound a bit silly for anyone to focus on such a seemingly minor question, but there is a good reason. When the Withdrawal Bill comes back to the Commons it will be to debate and decide on the 15 amendments which were approved by the House of Lords. With a hung Parliament, and divisions on various aspects of Brexit within both main parties, the arithmetic on some of those amendments is extremely close – and so the Government has tricky decisions to make on which it must defeat, which it believes it can defeat, and therefore how to proceed.

That political decision informs the timetabling of the Bill. If they Government was confident it would win every vote hands-down, it would presumably bring it back to the Commons straight away and swiftly put the Lords back in their box. The reason for bringing it back somewhat later is two-fold: first to give time to assess exactly where they stand on each amendment, and thereby decide the best course of action, and second to allow an opportunity to apply pressure to build majorities where possible. That approach is reasonable in the circumstances; if the timetable wasn’t just providing useful time but was actually slipping between the Chief Whip’s comments yesterday and the Leader of the House’s today, however, that would be rather worse, suggesting that ministers felt the situation was deteriorating.

As it is, it seems that the week of the 11th falls within the plan of ‘early to mid-June’, so the issues remain sticky but the situation isn’t in outright crisis (so far). The big decisions on each amendment are yet to be taken, and are being influenced by a variety of people across Downing Street, the Cabinet, Whitehall and Parliament. The implicit fact is that the Whips are not the decision-makers here, and have lost a great deal of authority – as one insider put it to ConservativeHome, “Julian Smith needs post-it notes to tell the difference between his arse and his elbow”.

The process of weighing the threat posed by each amendment and the prospect of defeating each is underway. Some are viewed as fairly harmless, if not beneficial or of great help, and might be conceded. The ‘meaningful vote’ amendment, however, is felt to be a direct attack on implementing Brexit at all and must therefore be fought. I’m told that the Duke of Wellington’s amendment deleting the date of Brexit from the Bill will also be opposed. Amendments that the Government argues are attempts on the part of the Lords to dictate how negotiations are carried out are viewed as a violation of constitutional principle, as well as practically harmful back-seat driving, such as the EEA amendment.

Some of the amendments under consideration require particularly careful assessment both legally and arithmetically, most notably that on the Customs Union. Some in government believe the actual wording of the amendment doesn’t tie their hands in the way that some on each side might hope or fear, and are therefore somewhat relaxed about it. However, there are twin concerns about the message it would send out if it were to pass (as ever, perception counts), and the risk that it might be further amendable to become something much worse. In either case, the safer approach is to kill the amendment off, which makes it a question of whether they have the votes.

Here there is a balancing act to perform. Pressure will be applied to would-be Conservative rebels, as you would expect. They will be reminded that the manifesto on which they stood only last year made a clear promise to leave the Single Market and the Customs Union, and that therefore this a question of their honour and their pledge to their associations and their constituents. That might persuade some, though it is unlikely to sway the most hardcore and co-ordinated Remainers, particularly if they do not intend to stand again.

Then there is the idea that this might be viewed as a question of confidence – the argument that rebellion might bring down the Government, spark an election, and perhaps even usher in Corbyn to Downing Street. Jacob Rees-Mogg has told ConservativeHome that this no longer works in the age of the Fixed-Term Parliaments Act, but the tactic will likely still be deployed. Indeed, there’s a belief that doing so will “burn off” some of the possible Tory rebels, even if it simply means converting them to abstainers.

That message must be used sparingly, however, because it is a double-edged sword. On the other side of the House are Labour Eurosceptics – the Dennis Skinners and Ronnie Campbells – who might be persuaded to vote with the Government on the principle of issues like the Customs Union but could be deterred from doing so if they fell they would be propping up a Tory Prime Minister in a confidence vote.

That cautionary note points to the ultimate, and hard to measure, truth about the forthcoming votes: they might well be decided by how the Labour Party divides. On issues like the EEA there’s a fairly strong expectation that enough Labour MPs will abstain for the amendment to be defeated. On the Customs Union the numbers are still so tight that the final decision on what to do will, I’m told, probably not be taken until the week of the vote itself.

It’s obviously difficult for a Conservative Government to influence Labour MPs on an issue – ConservativeHome urged Whips and Ministers to consider exactly that, and that is now happening. Pro-Brexit but anti-Tory MPs, like those already discussed, are tricky enough, but the really sensitive group on the Opposition benches is those MPs who might abstain in order to avoid angering their Leave-voting constituents.

It’s crucial to use the right approach towards the right people, or else you risk making things worse. Some Labour MPs in Leave-voting seats in the Midlands and the North, like Caroline Flint, already appear to be in a pretty good place, while some others are believed to be wavering and persuadable if sufficient pressure is applied. The newly-launched Conservative campaign site Respect the Result notably targets Labour MPs in exactly such constituencies; the logic is that such pressure might help to persuade some to abstain at the crucial moment, and for those who don’t do so it will generate useful data to help unseat them in future.