Watford have completed the signing of Nathaniel Chalobah from Chelsea on a five-year deal.
The 22-year-old has left the Premier League champions to move to Vicarage Road for an undisclosed fee.
Chalobah, who will wear the number 14 shirt, impressed during a loan spell with Watford during the 2012-13 season, scoring five times in 38 appearances in the Championship to help the Hornets to the play-off final.
He played just 15 times under Antonio Conte at Chelsea last season and the club's reported pursuit of Monaco midfielder Tiemoue Bakayoko prompted speculation that he would be allowed to leave.
The England youth international is Watford boss Marco Silva's sixth signing of the transfer window, following Tom Cleverley, Will Hughes, Daniel Bachmann, Jorge Segura and Kiko Femenia to the club.