Soccer Football - World Cup - Semi Final - Croatia v England - Luzhniki Stadium, Moscow, Russia - July 11, 2018 England manager Gareth Southgate looks dejected after the match REUTERS/Carl Recine
Not only has he rejuvenated an England side that had previously not reached a World Cup semi-final in 28 years, but he's also brought the waistcoat back from the dead.
British retailer Marks Spencer (M S) says its waistcoat sales have doubled since the World Cup began on June 14, and searches for the garment on its website are up over 100%.
Some customers even reported that M S waistcoats had sold out in some sizes.
"Gareth's sideline style has meant our waistcoats are really scoring with our customers with sales doubling since the World Cup began," an M S spokesperson said. "We've got enough different styles in stock for everyone to show their support for the boys."
EBay has also reported a 25% increase in searches for waistcoats and tailoring retailer TM Lewin tweeted that sales were "going through the stadium roof."
England's semi-final clash against Croatia has been dubbed "Waistcoat Wednesday" by leading blood cancer charity Bloodwise.
"As the whole country is gripped by football fever, and with Gareth's waistcoat-wearing having elevated him to the level of footballing fashionista, we thought that urging people to wear waistcoats on Wednesday would be a way of getting behind the boys at the same as raising money for a good cause," said Gemma Peters, chief executive of Bloodwise.