The 22-year-old captained Lee Carsley's U21 European Championship-winning side in 2023 and has found himself under him once again as he takes charge of the Three Lions as interim boss.
Speaking on his relationship with Carsley, the young defender admits he always knew he would play under him again.
“We’ve been on a good journey together," Harwood-Bellis said of his relationship with Carsely. "I’ve played the best part of four years for the under-21s.
“I’ve played a lot in the Championship but he always said to me that I would be close if I’m playing in the top league and delivering the same performances as in the Championship.”
The Saints star revealed the news to his father once he was named for this week’s Nations League squad and went on to say how proud his father was of him after years of hard work.
“Luckily, he’s called me up and stuck to his promise. My partner was there (when I found out). I told my dad (first). He was so proud. He was dead happy.
“I slowly led him into it and then told him. I asked him what he was up to, we had a bit of small talk and then I told him I’m going away with the seniors.
"He couldn’t believe it, probably as much as I couldn’t believe it."
Martin had nothing but praise for Harwood-Bellis who he believes is one of the best young talents in the Premier League.
"In the last couple of weeks, we've seen Taylor grow a lot as a character and leader on the pitch. He's taken a big responsibility, which he always has done for us with the ball.
"His mentality to defend, to head the ball, to be aggressive, to attack the ball at set-pieces is where he's become a real threat. He has to keep improving.
"I know he's trained in and around the squad before anyway when the under-21s have been used in training with the first team. I don't think he'll have any worries about that.
"Knowing Taylor, he'll just be desperate to get on the pitch and try and force his way into it. I'm really delighted for him."