Viral selfie

As part of the trip, Xi took a tour around the Etihad Stadium, Manchester City's ground, where the team's striker, Sergio Aguero, took a selfie with Xi and Cameron.

Aguero recalled: "We were at the training complex and the prime minister was there with President Xi. The president said to me, 'I remember you, you scored a goal.' We were laughing a little, and as we were walking along I felt confident to ask, 'Can I take a selfie with you?' The prime minister joined, and we took a selfie."

The Argentine striker posted the picture on Manchester City's official Twitter feed, writing in both Chinese and English, "Thank you for the selfie, President Xi."

He said he could never imagine what happened next. The selfie went viral, spreading across the world widely on social media.

"Every person in the world asks me about the selfie," he said. "It was really a beautiful moment that will live long in my memory."

Following Xi's visit, Manchester City has become one of the most popular Premier League clubs in China.

Later that year, China Media Capital bought 13 percent of the club's parent company, City Football Group, for 265 million pounds ($400 million), forging a close relationship between China and the club.

"We have a lot of interest in China and we also have a lot people and resources in helping China develop its football," Ferran Soriano, the club's chief executive officer, said. "We see China as a land of opportunity for global football."

He added: "There is no doubt that if China invests the right thing with the right patience, in 10 years, you will be one of the biggest football countries in the world."