Jacob Allmendinger had been saving for years — $13,000 set aside for a house deposit, a concrete step toward building his future. But when the World Cup came around, the 21-year-old from Hull, England, decided his grandfather was worth more than any down payment.

He spent every penny taking Geoff Golliker, 80, to watch England play in the United States and Mexico. They traveled from New York to Atlanta to the famous Azteca Stadium in Mexico City, where they witnessed a nail-biting 3-2 victory. They were on their way to the quarterfinals when something unexpected happened.

A company called Metawin, a crypto casino based in the US, had seen Jacob's story go viral on social media. The company made an unusual offer: if England beat Panama by more than two goals, Metawin would pay Jacob back all the money.

England won 2-0 — close, but not quite enough to clear the two-goal margin. Jacob figured that was that.

Then Metawin contacted him again. The company said it would still pay £10,000 anyway if England beat DR Congo. When England did exactly that, Jacob checked his bank account.

"I didn't quite believe it, to be honest, until I looked at my bank and it was there," he told the BBC. "I was just in shock."

The money Jacob spent had come from years of careful saving. Now, thanks to a stranger's kindness sparked by a social media post, part of it found its way back.

For Jacob, though, the trip was never really about the money. He started going to football matches with his grandad when he was just a little kid, cheering on their hometown team in Hull. Now, decades later, he wanted to return the favor.

"We get on like a house on fire," Jacob said. "We're more best mates than grandad and grandson."

The response to their story has been overwhelming. Jacob said people have reached out from all over — including some who lost their own grandparents and wished they'd done something similar.

"I think it just resonates with people," he said. "It just makes us cherish this time more, really."

As for the £10,000, Jacob said he'd put it in a savings account when he got home. "I could buy a house, anything is possible," he said.

England faces Norway next in the quarterfinals. Whether they go all the way or not, Jacob and Geoff have already had the trip of a lifetime — and a story that millions of people around the world are still talking about.