Celtic have completed the signing of David Turnbull from Motherwell.
The 21-year-old midfielder almost joined Celtic in June 2019 in a £3million transfer – which could have risen to £3.25million – only for a latent knee problem to emerge in the medical.
After proving his form and fitness in recent weeks following surgery, Turnbull sparked another bid from Celtic which has been accepted.
Motherwell said the fee was nearly double their previous transfer record – which was the £1.75million received from Celtic for Phil O'Donnell in 1994.
Turnbull told Celtic's website: "I'm absolutely delighted to be here, especially after what happened last year, and I'm ready to hit the ground running. I feel I've started well this season and I want to carry that on with Celtic.
"It's great to join the biggest club in Scotland and I want to help us win more silverware in what I know is an important season for Celtic."
Turnbull netted 15 goals in 30 league games in his breakthrough season and got off the mark in this campaign with a well-taken strike against Livingston.
Motherwell chairman Jim McMahon said he had mixed emotions over the transfer, which follows sales of the likes of Louis Moult, Marvin Johnson, Cedric Kipre and James Scott in recent seasons.
McMahon wrote on the club's website: "As chairman, I am delighted with this clear vindication of our strategy. For the health and prosperity of our fan-owned club, we must continue on this path.
"As a fan, I also feel the loss of such talented individuals who contribute to our success on the pitch. Everyone at the club does, particularly our manager. Stephen (Robinson) has performed phenomenally across his almost four years in charge.
"The money we receive for David will allow us in part to build up the strategic reserve, which helps secure and sustain us through such difficult and uncertain times.
"But this is also an opportunity to invest in the infrastructure, for example our training ground, academy and other facilities, with a view to providing an even-better environment for player development.
"We wish David every success for the future. He is a local boy who has supported this club all of his life and has given us many memorable moments on the pitch.
"His agreement to extend his contract is a testament to his integrity and in doing so he secured the club's interests as well as his own.
"As I've said above, as a fan, I regret to see him leave Fir Park. But the club can take pride knowing we have played a part in helping develop this exceptionally talented footballer and young man, whose legacy will endure for many years."
