Steve Sidwell has revealed his sadness at severing his close ties with Albion boss Steve Coppell.
The Seagulls' departed midfielder says Coppell has been like a "father figure" to him.
Sidwell completed a permanent move to Reading on Monday after five goals in 12 games for Albion on loan from Arsenal.
The 20-year-old also spent the whole of last season playing under Coppell when he was in charge at Brentford.
"He was like a father figure to me," Sidwell said. "I feel I'm a very loyal person. I don't like stabbing people in the back, but the chance to go to Reading was too good to turn down and I think Steve understands that.
"I've known him a long time. He's been great for me. I played at the same club as his son in the Sunday League.
"It's nice that he kept in touch throughout my career and I can't thank him enough."
Albion matched Reading's bid for Sidwell of a £75,000 downpayment rising to around £300,000, depending on other factors such as appearances and the success of the team.
Sidwell rejected a move to the Seagulls' relegation rivals Stoke, but Reading pay big wages and are pushing for the Premiership so a move to the gleaming Madejski Stadium proved irresistible.
Coppell said: "I always knew he was going to go on. His level of performance was such that somebody was going to take him sooner or later.
"I think everybody enjoyed his contribution and it's a blow because of the hole it has created in the team.
"It's not as if there is £300,000 in a pot available for me to spend. On that particular deal Arsenal were very flexible on the terms.
"We can't guarantee those terms being available should we do deals with other clubs."
Reading manager Alan Pardew has revealed Sidwell's form for Albion forced him to make a move earlier than he had planned.
He would have preferred to have left him on loan with the Seagulls for the rest of the season.
"In all honesty I didn't want to take Steve now, but the headlines he was grabbing on loan were just getting more and more clubs interested in him," said Pardew.
"I have wanted him for some time, but we have had to act quickly."
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