Scenario 1 Lipstick on a pig

Buoyed by his Brexit success (though much of the tough negotiation about Britain's future relationship would still lie ahead), Johnson would be free to call a general election in the spring or perhaps even sooner. He is likely to need his own mandate anyway, as the Tories' slim majority will make it exceedingly difficult to secure any major policy changes – including the tax cuts he is keen on. He would hope to strike quickly while the Brexit party's raison d'etre is undermined by Britain's departure from the EU, and before Labour's internal divisions on the issue are healed.

Johnson gives a triumphant party conference speech and, against the backdrop of enthusiastic support from his party – and with his agreement with EU leaders at one last European council meeting in Brussels – presses ahead with leaving on 31 October (or potentially asks for a short "technical" extension to finish the job of legislating for Brexit, though his "do or die" rhetoric about the Halloween deadline would make that politically difficult to pull off).

Johnson returns to parliament for a dramatic showdown. If he has opted for something like May's deal-plus, he will have to face down at least some of the "Spartans" who voted against the withdrawal agreement three times and who have backed his leadership bid. But he will also hope to win over many of those Labour MPs in Brexit-backing seats who believe the result of the referendum should be honoured. If against all the odds he wins a vote, there would then be a scramble to pass all the necessary legislation before exit day on 31 October: something many experts say is now impossible.

The new PM embarks on a whistle-stop tour of EU capitals including Dublin, charms Angela Merkel and Emmanuel Macron on the fringes of the G7 summit in Biarritz at the end of the month – and invites key Brussels decision-makers to Chequers to set out his Brexit stall. Somehow he secures minor concessions: perhaps the time limit to the backstop he rejected at one hustings event, but which some allies still believe could be sellable – plus a rewrite of the political declaration to emphasise a Canada-style free trade deal. He also stages a series of public speeches and events over the summer in a bid to show that the public back his approach..

Johnson appoints a fresh, united cabinet – and scrapes through a no-confidence vote (or avoids one altogether if Labour decide they cannot win it and hold their fire until the autumn). MPs disappear on recess for the summer, allowing his administration time and space to crack on with their Brexit plans.

Scenario 2 Canada dry

July Johnson hands key jobs in his new administration to those Brexit enthusiasts, including Iain Duncan Smith, who have been encouraging him to ditch Theresa May's deal altogether and plough full steam ahead towards the 31 October deadline. And he avoids a no-confidence vote – or scrapes through it, with even the Gaukeward squad giving him the benefit of the doubt until the autumn.

August As he meets EU leaders through the summer, Johnson explains that he wants to secure a standstill, so that the UK would leave as planned by November - but with a mutual agreement to continue existing trading arrangements for a short period, while a new, looser deal – and the all-important technical details about the Irish border – are hammered out. As he put it in a June interview, the details of the Irish border should not be "preordained by the backstop" but "remitted into the implementation period for discussion after we have left".

September MPs are given the opportunity to show their support (or not) for Johnson's plan, in the short parliamentary window at the start of September – and before the party conferences. Labour dismisses it as a "blind Brexit", but some backbenchers prefer it to advocating remain in a referendum to be held at some indeterminate future date. And EU leaders may perhaps prefer it to being seen to be pushing the UK out without a deal. If he wins at Westminster, Brexit happens on deadline and the UK is pitched into a standstill limbo, with a frantic period of negotiation ahead. If he is defeated, Johnson calls a swift general election, in the hope the public will give him a mandate to press ahead. (He could also call a referendum – but general elections are faster.)

October A snap general election campaign tightly focused, if Johnson gets his way, on whether Brexit should go ahead, with polling day perhaps a week before Brexit day. Labour opposes his Brexit plan but also seeks to switch the focus of the national debate towards transforming the economy, tackling poverty, and other issues on which Jeremy Corbyn has clear plans and a strong campaigning record. Meanwhile the Lib Dems under Jo Swinson seek to capitalise on their remain credentials. The outcome is anyone's guess.