West Brom midfielder Nigel Quashie has joined West Ham for an initial £1.5m.
West Ham will pay a further £250,000 if the Hammers avoid relegation this season or regain it in a season in which Quashie has been under contract.
The 28-year-old Scotland international has signed a three-and-a-half year deal with the Hammers and could make his debut against Fulham on Saturday.
"I want to thank Nigel for his contribution since I joined the club," said West Brom boss Tony Mowbray.
"Nigel recently expressed an interest in getting back to the Premier League.
"I want to reiterate that new players coming in doesn't mean I've got to let people go"
"When West Ham lodged their interest in signing Nigel, coupled with my desire to create some revenue to bring in fresh faces, I thought it was an opportunity which suited all parties."
Mowbray is expected to use the money as part of a bid for Hibernian midfield duo Scott Brown and Kevin Thompson.
Quashie has been relegated from the Premiership with QPR, Nottingham Forest, Southampton and West Brom.
He joined West Brom from Southampton during the 2006 for £1.2m and made 30 appearances for the club, scoring one goal.
The midfielder becomes boss Alan Curbishley's second signing following the arrival of Luis Boa Morte from Fulham.
"We've signed Nigel because he is an experienced player who will add competition to our central midfield positions," Curbishley told the club's website.
He added: "I have not promised him anything in terms of first team football - he will have to earn it like the rest of the players - but he brings vast experience to the club and has shown me that he is eager and hungry to do everything he can to help us.
"I want to reiterate that new players coming in doesn't mean I've got to let people go.
"The competition for places is a factor that will be important to us as we fight to move up the table, and it's up to every member of the squad to prove that they deserve to be in the starting line-up."