This could potentially pave the way for Malky Mackay to plunder Vicarage Rd once again with Alec Chamberlain a likely replacement.
Margetson was not placed on 'gardening leave' last week like the other backroom staff suggesting this move was already pre planned.
It's unsure if Margetson will continue as Wales goalkeeping coach.
Former Man City keeper Margetson earned one Welsh cap and has given Cardiff City 10 years service.
His first job in his new role will be to train the current West Ham stopper to face Cardiff City on August 7th.