Watford have completed the signing of Mike Williamson from Wycombe Wanderers for an undisclosed fee.
Williamson was left out of the League Two leaders' defeat at Bournemouth on Saturday, with Peter Taylor confirming the defender was discussing a move to Watford.
He would have been out of contract at the end of the season and Wycombe boss Taylor felt it was the right decision to accept the bid.
"Mike was out of contract and he expressed a desire to play in the Championship," Taylor told the club's official website.
"Unfortunately a Championship club wanted to buy Mike, he was out of contract in the summer and no one blames him for wanting to leave.
"I decided to recommend we accept the offer and let the sale go through.
"I've been really pleased with the way Mike has played during the opening half of the season and he helped us tremendously get us in the position we are in, but obviously I'm disappointed to lose him."
Williamson has signed a three-and-a-half year contract at Vicarage Road and ends Watford manager Brendan Rodgers' search for a commanding centre-half.
The former Southampton stopper made over 150 appearances for Wycombe and was the subject of a failed six-figure bid from Colchester United earlier in the transfer window.