With one obvious exception three thousand miles to the west of London, I refuse to believe there is anyone more ragingly insecure in global public life than Dr Liam Fox, the secretary of state for international trade, who persists in using his GP’s title nearly 25 years after being elected. What on earth is he thinking?

Whatever it is, he has been thinking it since 1992, when he left general practice to serve as an MP. Westminster’s loss was certainly Beaconsfield’s gain. His titular affectation takes you back to the unlamented era of rather beaten British villages where the local GP was so oddly powerful that you still deferred to him in the post office queue and had to give him a bottle of whisky every Christmas, even though he’d missed six opportunities to diagnose your wife’s cancer before it was too late.

Writing recently on the difference between the golden crop of postwar politicians and today’s, business academic Stefan Stern remarked: “Nick Clegg’s memoirs seem to reveal a young man slightly bemused by what he has been through and still struggling to understand what it all meant and how it happened. The Time of My Life by (Major) Denis Healey – beach master for the British assault bridge at Anzio in 1944 – reads differently.” Yowch. Still, which of us can really know the lingering pride of insisting, in a local surgery more than two decades ago, that the pain will eventually subside without antibiotics?

Unlike the current trade secretary, Denis Healey did not enter politics as Major Denis Healey. Retaining one’s rank in civilian life was regarded as not really done, doing so perceived by many as simply offering a signpost as to the type of character one was dealing with: namely, someone who was not to be entirely admired or taken seriously.

And so with Dr Liam Fox – though the clues to the man therein are by no means limited to this red flag. An expert in the self-inflicted wound, his attacks frequently miss their target in favour of reminding you of his own failings. A few weeks ago he declared that British export had grown “fat” and “lazy”, with executives unwilling to step up and do their duty because it would mean “they can’t play golf on a Friday afternoon”. A hilariously tin-eared stab at a motivational speech that served mainly to underscore the impression that Fox is the sort of Rotarian horror who’d literally sign a trade agreement wearing string-backed gloves.

Back when Theresa May appointed Dr Fox to his crucial Brexit role, I recalled my very first week at this newspaper, working on the Diary column. Our best story (and almost unquestionably our only thing approaching a story) concerned Liam’s decision to enliven a Westminster reception by telling a joke. “What do you call four dogs and a blackbird?” he inquired. “The Spice Girls!” Apologies for the repetition so soon, but it seems worth reminding people that a man who would tell that joke in front of journalists at Westminster in the year 2000 is now the chap whose judgment is trusted on reshaping our trade relationship with the world. If your expectations of his performance are not already commuted, do feel free to adjust them further now.

This week found Dr Fox snapping on his rubber examination gloves again, with two major speeches on trade post-Brexit – in the course of which he was forced to defend his golf comments. “When I was a doctor,” he explained, “my job was not to tell people what they wanted to hear. It was to tell them what they needed to hear so we could in order to put things right. If it applies to medicine, why do the same ethics not apply to politics? A question I have always wondered.” Always? I do hope he hasn’t lavished too much contemplation down the years on this somewhat slight philosophical point.

Still, his analogy does prompt a reworking of the old advice: general practitioner, heal thyself. Just as his effort at the World Trade Organisation had earlier in the week, the speech offered a chance for Dr Fox to showcase the limits of his vision, but ignore anyone trying to put him right. The UK will seek bespoke trade deals, he declared, though he failed to offer a clue as to what would be done until those were achieved. His address was composed largely of telltale generalities – “the glorious joy of free trade”; “a post-geography world”; “holistic” – and the lurches into specifics were even less well advised. Fox expected to see a post-Brexit EU deal at least as free as the one we have now: in a layman this might pass for puppyish optimism, but in the man in charge comes across as a mixture of arrogance and ignorance.

Though they didn’t quite put it this way, a parade of experts has since been on to tell Dr Fox not what he wanted to hear but what he needed to hear, so he can put things right. It goes without saying that he will ignore them. It is a mark of the posturingly insecure to do so.

Then again, his return to frontbench life itself is a triumph of mad optimism over good sense. Given the scale of misjudgment, the disgraced former cabinet minister Liam Fox should never have returned in any sane world. But Brexit has performed a questionable alchemy, allowing various of the politically undead to lumber out of the where-are-they-now files all the way back into key operational positions. Why would such a man not be given to delusion?

The language of his type of Brexiteer reminds me of nothing quite so much as the language of Spinal Tap on ceasing to be able to function as a touring band. As David St Hubbins observes, it is all a wonderful “freeing up”. “It’s a gift,” agrees bassist Derek Smalls. “It’s a gift of freedom … I mean, people should be envying us.”

If only the people envying the UK its current position weren’t so backward in coming forward. In their absence, we are stuck with the questionable gift of Dr Fox. The only guaranteed opportunity this seems to offer is the opportunity to prepare for his next collapse in judgment.

• This article was amended on 2 October 2016. An earlier version misnamed David St Hubbins as Derek.