Joe Rindl, BBC Sport
The Hammers were ruthless, playing devastating counter-attacking football to inflict their first league defeat on Brighton in the Premier League era.
They didn't dominate the ball - having just 19% of possession - but they never needed to.
Brighton will feel hard done by, but when it came to finishing, the Hammers took their chances and the Seagulls didn't.
The opener came through a scrappy James Ward-Prowse tap-in, the midfielder's first goal for the club.
And his impact on his teammates and West Ham's style of play is becoming more and more visible.
His finish was his third goal involvement in just his second game for David Moyes' side having joined from boyhood club Southampton this summer for around £30m.
That price tag might quickly start to look like a steal.