Reading midfielder James Henry has completed an undisclosed switch to Championship new-boys Millwall.
The Lions reached an agreement with the Royals on Monday and the formalities have now been pushed through.
The fee is not disclosed, but Reading have managed to negotiate a sell-on clause into the midfielder's contract.
Henry returns to the Den for the third time, having been on loan to Millwall in each of the last two seasons, and leaves the Madejski Stadium with Reading's best wishes, as they cannot offer him the first-team opportunities he needs.
"First and foremost, we would like to wish James the very best for the future," director of football Nick Hammond told the club's website.
"We have seen his development right through our academy, but the time has come where he simply needs to be playing regular first-team football.
"With the players we have here, we are not in a position to offer him the regular games he needs in order to get to the next stage of his development.
"Young players can come to this point in their careers and we have seen it with the likes of Simon Cox, they go on to other clubs and get the games they need, with a deal that also protects us as a club.
"James has grown both as a player and as a person during his time here at Reading, and he goes to a good club with our very best wishes."