Bertrand joins on loan
Bertrand, 19, has spent the last couple of season's out on onloan mainly at Norwich but with spells at Bournemouth and Oldham also. He is highly thought of at Stamford Bridge and Steve Coppell was interested in signing him last season but didn't act quickly enough and he went to Carrow Road where he was part of the side that got relegated from the Championship.
He signed for Chelsea from the youth set up at Gillingham with the West London side paying £125,000 for the services of a 16 year old, and has played 91 league games in his career so far.
He will wear the squad number 24 and will play his first game on Saturday in the friendly against Kettering.