Albion recorded their best win under Sam Allardyce with a five-star show at Chelsea.
After a bright start, it was Albion who fell behind when Marco Alonso's free kick rebounded into the path of Christian Pulisic after hitting the inside of the post.
But the game swung in the visitor's favour when experienced defender Thiago Silva was shown his marching orders for two yellow cards. Albion capitalised and drew level when Matheus Pereria dinked home after a Sam Johnstone clearance.
Pereira was at it again minutes later when he stroked the ball home after good work from Mbaye Diagne.
Callum Robinson then continued his scoring streak against Chelsea as he fired an unstoppable volley past Mendy in the Chelsea goal.
Albion extended their advantage again after a wonderful move down the left was converted by Diange.
Chelsea's second came from a close range finish from Mason Mount before Robinson capped off a memorable win with his second and Albion's fifth.
Watch all of the hightlights below:
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