Chelsea defender and England under-21 captain Jake Clarke-Salter has joined Birmingham on a season-long loan.
Birmingham said they beat off "significant competition" - including other Championship sides - for the 21-year-old, who watched the club's pre-season friendly at Bristol Rovers on Saturday.
He spent last season on loan at Dutch side Vitesse, and becomes the second player this month to make the switch from the Eredivisie to St Andrew's after former Arsenal midfielder Dan Crowley joined from Willem II.
Clarke-Salter joined Chelsea's academy as a nine-year-old and has had previous loan spells at Bristol Rovers and Sunderland.
Chelsea's Ethan Ampadu joined RB Leipzig on a season-long loan deal earlier this week, while Sky Sports News understands Crystal Palace are one of a number of clubs monitoring Reece James' situation.
James impressed on loan at Wigan last season, making 45 appearances.
Chelsea winger Callum Hudson-Odoi is close to agreeing a new contract at the club, which will be worth £180,000 a week.