Goalkeeper Sol Brynn has joined Leyton Orient on a season-long loan.
The Boro-born keeper spent last week with the first team squad in Portugal before heading straight to London to complete the formalities of his switch to the League One newcomers.
The 22-year-old had already signed a two-year contract extension with Boro at the end of last season which takes him up to the end of the 2025/26.
That came after a fine first full season of senior football for Sol, who spent last term on loan at Swindon Town.
Sol was voted the club's Player of the Season and he was an ever-present between the posts in the league campaign for the Robins.
He also won Swindon's Player of the Month three times over the year, and picked up a string of Man of the Match accolades.
Sol, a former England U18 international who joined Boro's Academy as a nine-year-old, also experienced senior football at Queen of the South where he made 21 appearances on loan during the latter half of 2021.