Pinnock, undetected by Chelsea’s defence, connected powerfully with a Mbeumo cross in the 58th minute, stunning the hosts who had spent much of the match buzzing around the Bees’ penalty area without creating many clear chances.

As the Blues poured forward in the 96th minute in search of a late equaliser, goalkeeper Robert Sanchez ventured up for a corner, only to be caught out when the visitors broke away and Mbeumo scored into an empty net.

Chelsea have now won only one of their last 13 home league matches, a dismal run stretching back into last season when they fired managers Thomas Tuchel and then Graham Potter.

The hosts started the West London derby on the front foot and winger Noni Madueke almost broke the deadlock in the first half when his curling shot hit the crossbar with 10 minutes on the clock.

However, Brentford soaked up everything Chelsea could throw at them with centre-forward Nicolas Jackson, back in the starting line-up after an injury, unable to provide much of a threat.

Brentford leapfrogged their neighbours into the 10th spot, while Chelsea dropped to 11th ahead of the rest of the weekend’s fixtures.