Keeper is back on loan for the rest of the season
The 24-year-old ‘keeper made 16 appearances for Blues in his first spell at the Club before returning to Upton Park in early January.
The paperwork went through to the football authorities tonight to beat the 11pm transfer window deadline.
Stephen, who joined the Hammers from Portsmouth last summer, will train with Town tomorrow morning and should be in contention for a place in the squad for the weekend game against Middlesbrough.
The deal had to be completed today because you are not allowed to go out on an emergency loan [outside the transfer window] twice to the same club in one season.