Kristoffer Ajer has signed a new contract, committing to Brentford until the summer of 2028.

In this extended interview, which was first published in May 2022, the defender looks back on his career so far - starting at the very beginning.

Kristoffer Ajer played his first game of football at the age of six.

Raelingen, his hometown club, won 30-0. Ajer was responsible for 26 of the goals.

Towering above the rest of the players, Ajer stood out from the very beginning.

“I started playing with my dad when I was four years old,” says Ajer, sat in the canteen at Jersey Road. It’s mid-afternoon and the chefs are packing away after another busy day of service.

“My dad wanted a son to play football with and I’ve always loved playing, so we started early!

“I’d already been playing for a few years by the time I was involved in my first game for Raelingen, so I’d developed a lot more than the other guys who had never played football.

“My dad was the coach, and he had a rule that every player on the pitch had to score at least once, so I scored 26 of our 30 goals!

“I remember I was refused to play the next matches of the tournament if I could not prove my age. After this, my mother always had my passport with her when I was playing!”

Head and shoulders above his peers at Raelingen – in every sense – Ajer moved to Lillestrøm SK at the age of 11.

But his time there would be short-lived. Ajer and his parents relocated to the city of Kristiansand on the southern coast of Norway in 2014. He was picked up by IK Start, which marked the beginning of his professional career.

Ajer continues: “I have two sisters who are 11 and 13 years older than me

“My oldest sister had her first child and my parents wanted to be closer to her, so that was the reason for the move.

“We had to move to a completely different part of the country. It was a difficult period for me – I had to move away from my friends – but everything worked out.

“I was between the B team and the first team at Lillestrøm, so it wasn’t a case of proving myself again at Start, because I hadn’t even done that at Lillestrøm.

"My aim at Lillestrøm was to break into the first team, so my objective didn’t change because I moved clubs. The goal was the same.

“IK Start were struggling financially at that time, so for my career it ended up being a perfect choice because I started playing in the first team almost straight away.”

Ajer made his professional debut for Start in July 2014 in a 2-1 win against Bodø/Glimt.

The following April, at just 16, he captained Start in a 1-1 draw against Lillestrøm. He is the youngest player to wear the armband in the Tippeligaen.

“That was an incredible moment,” Ajer recalls with a smile. “I’ve supported Lillestrøm my whole life. I walked out in front of my family and friends at the ground that I went and watched football at from the age of five.”

Ajer’s football career was taking off, but his feet remained firmly on the ground.

While playing professionally for Start, he attended high school in Kristiansand. A model pupil, he received 18 straight A’s.

“I was at school from 12 o’clock every day - I’d come straight from training," he recalls.

“The school and the club had a very close relationship; that’s why I was able to arrive later. I had private classes with the teachers to catch up on anything I’d missed.

“It was very important to my family that I had some structure at school, and I think that helped with my football as well; I had something else to focus on.

“I was naïve enough to say in an interview once that I was considering studying medicine alongside playing football! [Laughs] I realised pretty quickly that it wasn’t going to be possible; it’s a hell of a lot of work! I’ve since studied a few subjects just out of interest.”

Playing as a no.10 (more on that to come), Ajer found the net on eight occasions during the 2015/16 Tippeligaen season. His performances hadn’t gone unnoticed. In January 2016, at the invitation of fellow Norwegian Ronny Deila, Ajer had a trial with Celtic. It was a week that would change the course of his career.

On 17 February, he signed a four-year contract with the Scottish giants. He linked up with the club the following June.

It was a period of great change for Ajer – and not just in terms of geography.

“My parents lived with me for my first six months in Scotland, which meant everything," he admits.

“I had to transition from being a young boy playing every minute back home in Norway, to not playing a minute at Celtic.

“It was an important period for me to understand the rhythm of first-team football at a top club. For six months, I basically slept at the training ground.

“I worked so hard with John Kennedy, the first-team coach at Celtic. Next to my dad, he’s been the most important person for my development. He helped me so much.

“When I came to Celtic, I did a sprint test and did well. Brendan Rodgers wanted defenders who were comfortable on the ball, so that’s why the change happened.

“I grew up playing in midfield - I thought it would help with my development - but I always knew I’d eventually become a centre-half.

“Perhaps the transition happened a little quicker than I thought, but it was fantastic. Brendan has been so influential on my whole career. He was very clear on what I needed to do and the areas I needed to develop.”

A loan to Kilmarnock in January 2017 provided Ajer with the perfect opportunity to familiarise himself with Scottish football – and his new position.

“I loved it," he says. "My personality means that I always want to express myself. I want to be a character. I would never hide, even back then when I was 18 years old.

“Maybe people looked at me and thought I was too confident sometimes, but I wanted to express myself. Celtic is a different animal and a loan move really suited me at the time.

“It was a very nice dressing room. During that spell, Kilmarnock were bringing in a lot of young players on loan. Freddie Woodman and Sean Longstaff were both there at the time. One of my best friends today is Greg Taylor - I met him at Kilmarnock.

“I was able to live in the same flat in Glasgow while playing for Kilmarnock. On days off, I’d go back to Celtic’s training ground to analyse my games. It was a perfect set-up for me.

“When I arrived at Celtic, I weighed 82 kilos and had been playing as a no.10. I went to Kilmarnock and played a lot there as a centre-half. It was incredible. When I went back to Celtic in the summer, I was 95 kilos.”

Ajer’s loan at Kilmarnock was the perfect bridge into first-team football at Celtic. The 2017/18 season saw him become a mainstay in central defence.

In total, Ajer played 176 games and scored seven goals for Celtic. 38 of those appearances were in European competitions.

Celtic won the Scottish domestic treble in three consecutive seasons, 2017/18, 2018/19 and 2019/20, with Ajer named in the PFA Team of the Season in the middle campaign.

“That was an incredible time for me,” says Ajer, looking back on his five years north of the border.

“To walk out at Celtic Park in front of 60,000 people, to live in Glasgow, to win trophies with my good mates – it was a very, very nice time.

“It’s absolutely like living in a goldfish bowl! It’s 24/7 football in that city. Half the city really, really like you; half the city hate you!

“Winning the league at Celtic Park by beating Rangers 5-0 was my highlight. I had 25 family members in the stand that day, it was incredible!”

All good things must come to an end and, in July 2021, Ajer began a new chapter in London.

His blend of physical and technical attributes have made him an asset at both ends of the pitch.

And despite an impressive start to life in TW8, Ajer is convinced that he can reach a higher level: “From a defensive point of view, I’m put under more pressure here than I was at Celtic. Learning from the fantastic coaches, I already feel I’ve developed so much since signing for the Club.

“I respect Celtic so much, but in the Premier League you’re under pressure all the time. In every game, if you make a mistake the opposition will punish you. It’s very important for my development to experience that. It’s helped my game a lot.

“It’s been a perfect, perfect transfer. I know there are things I still need to develop, and I want to see how far I can take my career.”