The world seems to be spinning out of control into realms of fantasy, if not downright insanity. Fanciful notions and striking imagery overrule all else. Forget the boring but serious everyday business of fact-based government. When Donald Trump has a good chance of becoming US president and Boris Johnson is foreign secretary, globe-trotting in our name, then maybe all bets on rationality are off.

Within its first week back, on 11 October, parliament will be debating Brexit: no, not the plodding details of what the hell to do next, but whether Brexit means it’s time to bring back the royal yacht Britannia. Requiring a crew of 240, the 1952 floating palace has a state drawing room and state dining room for entertaining dignitaries around the world; it is a place, the Queen once said, where “I can truly relax”.

Why do we need it? The Conservative MP Jake Berry, a close Boris Johnson ally, says it would be a floating embassy to help the UK strike new post-Brexit trade deals around the world. Liam Fox would sail in her too, as he calls on foreign potentates: only last week he was on bended knee to Gulf dictators seeking the new trade bonanza he promises.

How much more fitting for him, and indeed for Boris, to woo such people with a visual reminder that Britannia rules the waves. British magnificence is what we do best. Berry tells the Sun: “It could bring in billions of pounds worth of trade deals for post-Brexit Britain.”

In this miasma, gestures and dreams can ignore the terrible prospect of years of brain-crunching negotiations on every detailed aspect of trade and regulation for every product and service, which might take not two but 10 years of soul-destroying and pointless agony, distracting from all the country’s other pressing problems. And a good result of all this would be merely to end up no worse off.

The usually diplomatic Institute for Government has just delivered a devastating warning on how unprepared and chaotic the government’s approach has been so far, condemning the bizarre division of Brexit between three new departments(led, though the report doesn’t say so, by three erratic, vain men). This means hiring 500 more civil servants – and they need to be big-brained – costing some £65m.

Already Theresa May has had to slap the three down for grandstanding turf wars, declaring for a hard Brexit before she has said anything at all about her approach. We have no idea what she intends – because, says the report: “There is a gaping void in the government negotiating strategy.”

Meanwhile the rest of the world looks on at our pantomime politics with bemused perplexity, irritation or mockery. Best was the utter incredulity of the European parliament’s chief Brexit negotiator, Guy Verhofstadt, at the sheer nerve of Boris Johnson promising Turkey to be its strongest advocate for joining the EU.

“So Boris Johnson wants to help Turkey join the EU – after he just campaigned for the UK to leave the EU on the basis that Turkey would be joining the EU in the near future,” he wrote on Facebook. Just remember all those warnings of Turks poised at our borders.

Next Verhofstadt rightly walloped our defence secretary, Michael Fallon, for vowing to stop the EU setting up its own army. “The UK defence minister says the UK government will block EU efforts to enhance its security capabilities, even though the UK is leaving the EU – yet they say they want an enhanced security relationship with the EU after Brexit.”

And then he went for the international trade secretary, Liam Fox, who he said had “indicated the UK will leave the EU’s customs union because he thinks other markets are more important – while his prime minister tells us the EU27 ‘will sign’ an ambitious trade deal with the UK”. Politics, he said, “never fails to surprise me”.

Indeed, it astounds many of us in Britain too. Slap-downs abound from EU leaders at the sheer unreality of British ministers’ fantasies about the deal they pretend they can get.

The royal yacht will almost certainly stay in its dock in Leith, where tourists flock to this relic of the dying days of empire. In dry dock too is any coherent plan, any shred of an idea of what Brexit means, as all the old leave campaigners and their press clamour for a quick “hard” exit, calling anything less a betrayal of the voters.

Meanwhile the Society of Motor Manufacturers and Traders said yesterday that with 80% of cars from many UK plants selling to the EU, an industry supporting 300,000 jobs would be “jeopardised if we are not in the single market”.

But oh, let’s debate the royal yacht instead – much easier and more fun. We are no longer a country to be taken seriously.