Brentford have signed Kristoffer Ajer from Celtic, with the Premier League new boys paying a club record fee of £13.5m for the Norway defender.
Ajer completed a medical before signing a five-year contract, with the deal subject to international clearance.
The 23-year-old joined Celtic shortly after his 18th birthday and spent the second half of his first year in Scotland on loan at Kilmarnock before becoming a first-team regular.
Brentford head coach Thomas Frank said: "We wanted to get another central defender in and Kris was our first choice. We think he fits the position-specific profile perfectly, especially on the ball.
"Kris is very composed and can find the right passes between the lines. His level when bringing the ball forward is very high.
"As a defender he has the physicality that you need and he won his duels when he played in the Scottish league. He can help us in both boxes, with his strength in the air.
"He is a player at a good age and we think he (can) come straight in and be ready to perform in the Premier League. But he also fits the way we want to recruit players and work with them. He can develop as a player and both Brentford FC and Kris can move to a higher level in the coming years."
Sweden defender Carl Starfelt appears to be a like-for-like replacement, with the Rubin Kazan player joining Celtic today on a four-year deal.
Starfelt, 26, who had been with Russian side Rubin since 2019, is the Hoops' third summer signing.
A statement on Celtic’s official website said: "Celtic Football Club is delighted to announce that it has reached agreement with FC Rubin Kazan for the transfer of Swedish defender Carl Starfelt, subject to the satisfaction of usual conditions and international clearance.
"On satisfaction and gaining clearance, Carl will sign on a four-year deal.
"Carl will also be subject to standard quarantine protocols and will join the squad as soon as possible."
Former Gothenburg defender Starfelt was not included in Sweden’s squad for Euro 2020, but played the full 90 minutes in their home friendly win against Estonia in March.
Celtic manager Ange Postecoglou added: "I’m really pleased agreement has been reached and we are really looking forward to Carl joining up with the squad. Carl is an experienced player and someone with the attributes to be a real success at Celtic.
"He is a strong, athletic and committed defender and will add quality to our squad. I am sure he will be a player our supporters will welcome warmly and someone who will be really important for us going forward."
Celtic signed Japan international forward Kyogo Furuhashi and Israel international Liel Abada earlier this month.