The 27-year-old defender admitted that his split from Birmingham, where he's spent the last four years, was acrimonious, however he insists he is ready to give full commitment to his new club.
“I'm very pleased that the deal is now done. I feel it is a very positive move for me and I am delighted to be back playing in the Premiership again.
”The situation with Birmingham was a difficult one, but this was a fantastic opportunity for me and I'm delighted to be a West Ham United player. The club may not be in a comfortable position at the moment but I am sure that will change soon.” Upson told the official site.
Hammers boss Alan Curbishley was overjoyed at finally getting his main transfer target after weeks of discussions with a reluctant Birmingham City board.
“I'm delighted that we have brought Matthew to the Club. He is a player I have admired for a long time and someone who, once again, has demonstrated that he wants to be a part of the Club and its future.
”He has got the experience, the personality and, above all, is a very good player. I'm sure our fans will see that, and I am sure he will play a big part between now and the end of the season.” said Curbs.