Peterborough assistant manager Mark Robson has left the club to join West Ham'scoaching staff.
Robson, 52, who had worked alongside Peterborough boss Darren Ferguson since August 2020, has been appointed as the Premier League club's Under-23s manager.
The former midfielder played for the London Stadium side in the early 90s, notching up 47 appearances.
Posh under-23s manager Mark Etherington will step up to fill the role vacated by Robson.
Ferguson told Peterborough's website: "It's never ideal to have to make a change within the management structure midway through the season. So the changes that have been made are designed to make as minimal impact as possible and we'll see how it goes as we move forward."
Speaking about the move, Robson - a lifelong Hammers fan - told the club's website: "I’m really pleased to be joining the academy and really pleased to be back at West Ham United, my local team.
"I’ve been a supporter all my life, watching from the terraces and playing for the club, so to have the chance to come back and be a part of the process helping our younger players on the pathway to the first team is fantastic. I’m really looking forward to the new challenge."
Former West Ham and Charlton midfielder Robson returned for a second spell atPeterborough when he teamed up with Ferguson, having been head coach at the clubin 2011 when they won promotion to the Championship.