Marko Arnautovic's first West Ham goal secured a 1-0 victory over Chelsea and a first win for manager David Moyes.
Arnautovic struck after only six minutes to condemn the champions to a first defeat in seven Premier League matches.
The £24m club-record signing was jeered by home fans earlier in the season after some below-par displays, but he looks a player reborn under Moyes.
In fact West Ham look an entirely different side to the shambles they appeared towards the end of Slaven Bilic's spell in charge.
Moyes showed he is not one to shy away from tough decisions, and dropping England goalkeeper Joe Hart in a World Cup year was certainly a big call.
But Hart's replacement, Spanish 'keeper Adrian, justified his selection with fine first-half saves from N'Golo Kante and Davide Zappacosta.
Hit play on the video above to see the match highlights.