Now 31 and settled at Real Betis, the Spaniard lined up against Arsenal for the first time on Wednesday, a meeting that had eluded him even on loan at Sporting, when a precisely timed knee injury ruled him out of a previous fixture between the sides. Betis thumped the Gunners 3-1 in Dublin.
Speaking to The Guardian's Sid Lowe before the match, Bellerín described his emotional connection to a club he represented for a decade.
"I still feel them as a family. London gave me that space to explore my world, to mature," he said. "There are places that can limit you, but London was a place where I could expand, explore life."
He remains close to several figures still at the club, chief among them Mikel Arteta, his former team-mate and now Arsenal's head coach.
Bellerín was just 16 when he arrived in the English capital from Barcelona's academy, and recalled the sense of independence the club instilled in its young players.
"The first thing Liam Brady, the academy director, gave us was an Oyster card. We earned €400 a month, but we had a sense of independence. We didn't feel overprotected or abandoned. We had to catch two buses and the Tube to get to training," he said, adding that he lived in numerous different places across 12 years in the city, including a 17th-century farmhouse in St Albans that could only be reached by a sand track.
He spoke warmly of Arsenal's Premier League title win last season, which ended a 22-year wait for the club.
"One of the most beautiful things when they won the league was that a lot of people sent me messages and I felt part of it," he said. "There are so many people I talk to, we're all Arsenal fans, and it was like a release, a relief after so long."
On Arteta's influence over his career, Bellerín said: "I was with him a year and a half as coach and I could say that 80% of my football came through Mikel's mind. His is a totally different vision. There's an understanding, an observation, he sees patterns, and has a very specific language. I'd go so far as to say that he has put extra years on my career."
Asked about his decision to leave Arsenal, Bellerín described it as more of a gradual disconnection than a single moment.
"There's no specific reason. Something happened, but it's not anything concrete; it's more a kind of disconnection where I felt I could no longer help the club and the club could no longer help me. We resolved it in the friendliest possible way. Maybe I needed to be close to my roots, to home. When you leave a club like Arsenal, it's scary. It hurts."
He said settling into life at Real Betis had been eased by the dressing room he found in Seville.
"What struck me most was the dressing room. There's something horizontal in the relationship with other staff members. That didn't exist at my other clubs. That's our essence, what keeps us together. And it fits with my values."