His promotion to style icon, the England manager was credited with inspiring a 35 per cent increase in sales of said garment during the summer, was one of the World Cup’s more unexpected turn of events.
About on a par, in fact, with the Three Lions reaching the semi-finals for the first time in 28 years to earn the adulation of a country that had long since tired of its under-achieving and over-paid footballers.
Rarely had England flown out to a major tournament with such low expectations as was the case in June when Southgate and his men headed to Russia.
Five weeks later, however, and those same players were rightly being lauded as heroes on their return to these shores.
Whether that summer of love for the national team proves to be a blip a la 1990 or the start of something big remains to be seen. The first clues will come on Saturday night as Spain come to the capital for the start of the new Nations League.
The waistcoat may, indeed, be missing but what Southgate will not be discarding is what turned his side from zeroes to heroes in the eyes of the nation.
Hard work, humility and a system that the players both understood and bought into took England a long way.
Sure, a Croatian team who looked superior on paper certainly proved to be that on the pitch to deny Southgate the honour of joining Sir Alf Ramsey as the only Englishman to lead his country out at a World Cup final.
But by laying the ghosts of penalty shoot-outs past against Colombia and cruising past Sweden in the quarter-finals with ease, this team has shown it can deliver on the big stage.
Expectation is up. There is no getting away from that. A team cannot reach the last four of a World Cup and still expect to be treated as underdogs.
What will be fascinating is whether a solution has been found to the shortcomings that were exploited so ruthlessly by Croatia in the Luzhniki Stadium.
When the pressure was truly on, Southgate’s men were guilty of regressing to the hit-and-hope football that had so characterised their struggles in previous tournaments.
The high pressing of the Croats led to what was an unwitting shift in emphasis from the passing game that had proved so effective against Panama, Colombia and Tunisia.
Where against those lesser lights England had controlled both possession and the match, this time Southgate’s men were simply over-run both out wide and in the middle.
Ivan Strinic and Sime Vrsalijko were the catalysts by pinning back Kieran Trippier and Ashley Young sufficiently to turn what had started as a three-man backline into effectively 5-3-2.
This, in turn, allowed Luka Modric, Marcelo Brozovic and Rakitic to seize control of midfield as, first, England’s composure went and then any hopes of reaching the final.
Spain’s new coach, Luis Enrqiue, will have watched this and planned accordingly for the Nations League opener at Wembley.
It is a shame Adam Lallana’s injured groin means he is missing once again. When England needed to battle against Croatia, Dele Alli and Jesse Lingard, both more used to getting on the end of attacks than breaking up those of the opposition, were found wanting.
Jordan Henderson, as a result, was left with simply too much to do and the centre of the park was lost and England’s only hope became trying to engineer a race between Raheem Sterling and the Croatia defence.
A Spanish side still smarting from crashing out in the first knockout stage to hosts Russia will be encouraged by Sterling’s absence through injury.
That poor showing at the World Cup by Spain led to accusations back home that a desire for perfection among a much-vaunted squad had led to insipid play.
Enrique faced similar rumblings on taking over at Barcelona but responded by winning the treble in his first year with a much more incisive style.
It will be a big test for England, not least because of a point made by Southgate amid the euphoria of his side’s performance in Russia.
“We have to be realistic,” said the Three Lions chief shortly before packing away his waistcoat and heading off on holiday. “All the games we have had against the bigger teams, we haven’t managed to win.”
Victory at Wembley, of course, would put that right and ensure the feelgood factor surrounding the Three Lions in Russia extends deep into the autumn and, hopefully, beyond.