‘The thing about the greased piglet is that he manages to slip through other people’s hands where mere mortals fail.’

That was the wry assessment of Boris Johnson, given last autumn by David Cameron who has followed the Prime Minister’s brilliant career since their schooldays with many a chuckle and shake of the head.

A week or so ago it seemed as though the piglet had finally been cornered. Authority was ebbing away in the wake of Johnson’s chaotic imposition of a second nationwide lockdown. The decisive shift in the polls which Keir Starmer had been waiting for appeared finally to be happening.

And then, on Monday, came the Pfizer announcement that its vaccine worked, with an amazing 90 per cent effectiveness rate. Not only that, but it worked in a particular way that raised expectations that several other vaccines in development will work too.

The animal spirts of investors stirred and the stock market roared – the FTSE 100 rose by 300 points in a few hours. Professor Sir John Bell, a government scientific adviser, declared ‘with some confidence’ that people could look forward to getting back to normal by spring. ‘Yes, yes, yes,’ Sir John told Radio 4 in the manner of a regius professor re-enacting the famous diner scene in When Harry Met Sally.

All over the country the idea that we could march into 2021 to the strains of ‘Come on baby let the good times roll’ landed well. Hope soared for a Roaring Twenties of our own – just a year late to arrive.

With new economic data showing GDP growth of 15.5 per cent in the third quarter (before the resumption of very restrictive social distancing measures), the potential for this year’s economic contraction to be wiped out became more obvious too.

Sure, the economy is probably shrinking again right now because of November’s lockdown. But if we can bounce back so strongly on a wing and a prayer and Rishi Sunak’s meal deals, just think what the UK economy could do with the certain knowledge that Covid has been conquered by medical science.

This bleeds into something else too: if 2021 is to be marked by a rapid rebound in growth, then any impact of ending the Brexit transition period without a trade deal is going to be swamped by good news.

Remainers will be left pleading for everyone to agree that the record growth we are experiencing would be another half a per cent higher if we still had frictionless trade with the EU. Big deal.

The potential for a Boris Johnson political resurgence in such a climate is obvious. Both the Covid months and the Brexit years will be securely in the rear-view mirror – though undoubtedly there will be after-shocks from both.

A smart new team of advisers mainly pinched from Rishi Sunak will be hitting their stride and a Cabinet reshuffle can bring back those ‘grown-ups’ previously exiled due to their nasty bouts of Europhilia. Perhaps the combination of these two events will help to correct the fault in Mr Johnson’s ‘method’ that I wrote about last week, leading to a better-briefed leader taking more care with his undertakings.

In this golden scenario, naturally England will go on to win the European Football Championships and the Prime Minister’s talent for placing himself at the centre of good news will see him take part in numerous photo-opportunities that will raise a smile among the politically non-aligned and remind them of that glorious Olympic summer of 2012. Perhaps the PM will even get around to marrying his girlfriend – after all, they became engaged at the end of 2019.

Now, many of the happenings envisaged here may well not come to pass. One or two are even stretching the bounds of credulity. The England football team, for instance, is far more accustomed to being bridesmaid than bride.

But the point stands that, post-Pfizer, one should expect 2021 to be a much happier year than 2020 has been and that much of it will be taken up with bounce-back growth. Where Johnson’s pledge at the end of April to ‘fire up the engines of this vast UK economy’ was thrown off course by the second wave of Covid, he would be extremely unfortunate to run into head winds of similar strength again next year.

So how might Keir Starmer fare in good times? Instinct says not terribly well. His favoured technique is to be the Mr Serious who berates the PM for things having gone wrong due to a lack of technocratic knowhow.

A balanced assessment tells us that Johnson has been badly exposed this year in the most trying of circumstances. But somehow he is still standing and his personal polling is not so dire as to be irrecoverable. If he mucks up in good times too, there will be nothing much to be said in his favour. But, for now, the piglet once more runs free.