MK Dons have signed Cambridge United defender Harry Darling for an undisclosed fee.
The deal for the 21-year-old also includes a sell on fee.
Darling, 21, came through Cambridge's academy and made his debut as a 17-year-old against Scunthorpe United.
The centre back has been a virtual ever present for the U's this season, helping them reach the top of League Two, but with his contract due to expire in the summer, the club have now decided to cash in.
“Harry goes with our very best wishes, we are proud of his progress, grateful for his contribution across the club and excited by his future," Cambridge boss Mark Bonner said.
“This now opens playing opportunities for other players and we will add the appropriate competition and cover to our squad in due course, to enable us to continue competing at the level we have been.”
MK Dons manager Russell Martin said Darling was their "number one" defensive target.
“Harry is a player we have been keeping tabs on for some time. We’ve watched a lot of him, particularly in the last few months and he’s been our number one target at this position.
“It’s a significant deal for the Football Club and it’s an important signing for us, short term and in the long term as well. We’re delighted to get it over the line.”
Meanwhile, Northampton Town winger Nicky Adams has joined League Two side Oldham Athletic and teammate Harry Smith has moved to Scottish club Motherwell on loan for the rest of the campaign.