YOU could tell by the tone of the “anonymous” leaked memo outlining the government’s thinking on the Brexit negotiations: Boris and his pals – the source was obviously the prime minister’s right-hand man Dominic Cummings – are rattled. Very rattled.

“If you don’t give us what we want we’ll be very, very naughty!” screamed the memo, which outlined the ways in which the UK would seek to punish EU states that agreed to give the UK an extension, should a deal not be reached by October 31. Putting such countries at the “back of the queue” for a trade deal and withdrawing defence and security co-operation were mooted, as was refusing to co-operate with and ratify EU business. Elsewhere, there was talk of getting Hungary’s populist right-wing leader to vote against the extension (all 27 members must agree). How Angela and Emmanuel must have creased with laughter as they read all this tosh, not least because the threats show how little Cummings understands – or admits to understanding – about how the EU works.

Brexit talks move to final phase after 'breakthrough'

Not that this was aimed at an EU audience, of course. No, Big Bad Dom’s hysterical hardman nonsense was for the benefit of the home crowd, yet another attempt to attribute blame for the failing “all or nothing” approach that is being thwarted at every turn. Looks like Cummings could be running out of dead cats to hurl.

The memo also highlights that despite all the trash talk, Johnson sees no way around the extension contained in the so-called Benn Act. That’s probably why the mood music became more upbeat during the latest round of talks with Irish Taoiseach Leo Varadkar; trying to get a deal is simply Johnson’s next roll of the dice. The prize he truly covets, of course, is a majority in parliament; whether that happens off the back of a deal or no-deal is a mere moot point to this reckless PM.

Despite a move to substantive negotiations, there is still no guarantee that a deal can or will be struck with the EU. But if Mr Johnson does manage to wrest an agreement that the EU and Ireland can live with – one which will, in yet another surreal and eye-rolling twist to the Brexit debacle, basically be Theresa May’s deal all over again – it creates a dilemma for the opposition parties.

How should they respond to a potentially dangerous situation wherein the PM gleefully passes the buck to MPs, daring them not to ratify his deal as the clock ominously ticks down, setting up the next play in his intellectually bankrupt but politically expedient blame game?

Yet again, Nicola Sturgeon has shown sense and leadership by making clear that her MPs will not vote for it. Why would they? Ms Sturgeon has been consistent from the outset: her party will not vote for any deal that takes Scotland and the UK out of the single market and customs union, causing untold damage to the Scottish economy. And since the current prime minister favours a harder, more isolationist and ideologically right-wing Brexit than even that fashioned by Mrs May, it is surely incumbent upon all UK opposition parties to fight tooth and nail to save the country from such a disastrous and divisive path.

That’s why they have no option but to vote down Mr Johnson’s deal and force a general election, the circumstances of which will be vital in determining how it can be framed. After all, it’s not just Mr Johnson’s tenure that must be keep short, but his list of options.

The Lib Dems under Jo Swinson won’t vote for any deal, not least because “getting Brexit done” would render their new "stop Brexit altogether" mandate redundant. And though it’s perhaps inevitable that some of the rebel Tories sitting on opposition benches might end up voting for the PM’s deal (most ratified Mrs May’s version) others might decide to stick it to their former party and put the interests of the country first, especially since they are likely to lose their jobs anyway. The DUP, shafted by Mrs May, look set to be sold-out by her successor, too, and will vote against.

It’s Labour we have to worry about, particularly MPs representing Leave-voting areas that may be willing to fall into a Boris-shaped trap, voting through a deal that would allow the PM to take personal credit for “getting Brexit done”, handing him victory and a key element of their campaign. Would they be that stupid? I fear they would. It would be a cruel but perhaps not unexpected irony if Labour enabled a devastating hard Brexit to be foisted upon our poorest people.

There is, as yet, no deal to put to parliament. But Boris looks increasingly frustrated and desperate. His options are running out. Time for opposition MPs of all colours to truly exploit this by working in a more disciplined way to close him down completely. We will simply never forgive them if they don’t.