Watford came from two goals down to stun West Ham United in a 4-2 victory at the London Stadium this afternoon.
In the first half-hour of the game, it looked as though the Hammers were destined for a comfortable triumph at their new stadium.
Michail Antonio caused plenty of trouble as he forced a save from Heurelho Gomes in the first minute after cutting inside from the right.
The shot-stopper had to be alert in order to stop the follow-up shot from Dimitri Payet, who was influential for the Hammers in the first half.
The first of the six goals came in the fifth minute when Antonio met Payet's corner kick in the box and headed the ball home from six yards out.
Watford squandered an opportunity to equalise instantly when Roberto Pereyra found Odion Ighalo and the forward's close-range effort went wide.
The match was end to end in spells, but it was West Ham who extended their lead when an audacious rabona from Payet perfectly dropped on the head of Antonio, who headed the ball past Gomes from three yards out.
The tide began to turn just before the half-time break when Ighalo cut inside from the left before unleashing a shot from outside of the box.
The ball took a significant deflection off James Collins, which Adrian could not have been prepared for, and the ball trickled into the back of the net.
Troy Deeney played a pivotal role in the comeback as he made the most of a moment of confusion between Collins and Adrian by nicking the ball and chipping it past the keeper seconds before the half-time whistle.
The visitors began the second half on the front foot and were rewarded for it when Pereyra chipped the ball to the far post, where Etienne Capoue was waiting to send a half-volley into the corner of the net.
The comeback was completed in the 63rd minute when Capoue pulled the ball back to Jose Holebas, who scored the fourth and final goal for Watford from the edge of the danger area.
West Ham have suffered three defeats and recorded just one win in the Premier League so far this season, while the Hornets have claimed their first win of the campaign.