The Hammers had not beaten the Seagulls since their promotion to the Premier League – a run that spanned six years and 12 games.
However, goals from James Ward-Prowse – his first for the Irons and 50th in the Premier League – Jarrod Bowen and Michail Antonio secured a fine victory for David Moyes’ side.
Alphonse Areola was in inspired form for the Hammers but was finally beaten when Pascal Gross found the corner with an inch perfect strike from outside the box, with ten minutes remaining.
Evan Ferguson and Lewis Dunk went close in injury-time but it was too little, too late for Albion, who were a shadow of the side that dismantled Wolves and Luton.
Here’s how Roberto De Zerbi’s players rated:
Alphonse Areola was in inspired form for the Hammers but was finally beaten when Pascal Gross found the corner with an inch perfect strike from outside the box, with ten minutes remaining.