West Ham sign Sunderland manager Gus Poyet's son Diego

Poyet, 19, becomes the club's fourth summer signing following the arrivals of Argentine striker Mauro Zarate, Senegal midfielder Cheikhou Kouyate and defender Aaron Cresswell.

No financial details were given.

The Spanish-born midfielder represented England at under-17 level and was second tier Charlton's player of the year last season despite not making his debut until January.

"It's massive to come to a Premier League club," Poyet told the club's website. "I wanted a new challenge and soon as I heard there was a chance of stepping up I had to take it."

(Reporting By Tom Hayward, editing by Alan Baldwin)