Roy a Hammer now

The Northern Ireland international spent four years at the Old Trafford club, after a 2.5million pound (3.5million euro) transfer from Wigan in the summer of 2001.

Carroll had finally established himself in United's starting line-up after USA international Tim Howard's dip in form and confidence, but a series of high-profile errors made Sir Alex Ferguson reluctant to assure him first-choice status.

However, West Ham have only one fit senior 'keeper on their books, Stephen Bywater, after Jimmy Walker suffered a serious knee injury in May's play-off final victory.

Manager Alan Pardew also believes Carroll's experience at the highest level will also be of value to West Ham as they try to retain Premiership status.

"The injury to Jimmy Walker in the play-off final was a real hammer blow for us," explained Pardew to the club's official website.

"I've moved quickly to rectify that situation by signing Roy Carroll, who is an established Premiership goalkeeper.

"Roy comes to West Ham United in his prime and because of his association with Manchester United will not be fazed by the size of this club.

"I believe Roy's best years are ahead of him and when a club is re-introduced to the Premier League, as we are, goalkeeper is an essential position.

"Roy brings all the qualities we need for the coming campaign and we're delighted to have him as part of our squad.

"This will be the first of what I hope will be three or four more signings to strengthen the team for the challenge ahead."

Carroll, 27 years old, started his English league career at Hull and made 34 appearances for Man United last season.