Kristoffer Ajer, born in Norway on 17 April 1998 (age 28), came through at Start before Celtic paid around £750,000 for him in July 2016. His most productive league season had already come in 2015, when he scored eight goals in 28 appearances for Start – useful early evidence that he was not just a tall centre-half standing in the right places.
At 6ft 5in (1.96m), Ajer was always an imposing defender, but his Celtic development needed senior football as much as patience. An early loan spell helped sharpen him up before he became a more regular part of the first-team picture in Glasgow. He grew into an important Celtic player: sometimes raw, often ambitious in possession, and rarely short of self-belief.
He left Celtic in July 2021, joining Brentford for around £14m. That was a substantial fee by Celtic standards and a fair reflection of the player he had become by then. In England, he had to work through the usual adjustments rather than stroll into comfort, but he has remained part of Brentford’s Premier League group.
In 2025-26, Ajer is still a regular first-team presence at Brentford, with 27 league appearances, plus one in the FA Cup and three in the League Cup. He has also stayed involved with Norway, making eight appearances in European World Cup qualifying and scoring once. His market value is around £15.5m, according to Transfermarkt.
He was linked with a move to Celtic in June 2025, while still at Brentford. As it stands, his career runs clearly enough: Start gave him his platform, Celtic developed him into a saleable and significant defender, and Brentford have kept him operating at Premier League level.
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