After all the concern about extra security for their supporters it seemed Chelsea had forgotten all about protecting their own goal as West Ham won the first London derby at their new home.
Cheikhou Kouyate fired the Hammers into the lead and Edmilson Fernandes grabbed a second to claim a place in the last eight of the EFL Cup.
Antonio Conte paid for making seven changes to the team which impressed against Manchester United, four days earlier, and discovered the limitations of this squad.
Chelsea struggled to find a way back into the tie and Conte replaced the young players he hoped might take some experience from the occasion when sending on Diego Costa, Eden Hazard and Pedro in a late bid to rescue the game.