Terry's defence caught out as West Ham find form
West Ham 2 Chelsea 1
West Ham have been waiting for a victory such as this to mark the start of the era of what they are legally obliged to call the London Stadium and here it was at last, a resounding cup win over old rivals from the west that felt like one they might have enjoyed at Upton Park.
Slaven Bilic's team are in the quarter-finals of the League Cup and, while the action might have taken place a lot further away from the crowd than it ever did in their previous home, there were hallmarks of a classic West Ham win.
The opposition were that much more famous and more expensively acquired but they fell prey to a team with a greater urgency.
There was none of the pre-match fighting that had been a concern but during the game there was coin-throwing inside the stadium, and then plastic bottles and seats were thrown towards the end of the match as hundreds of fans were involved in ugly scenes.
The first goal from Cheikhou Kouyate set the standard and Chelsea never truly recovered from the second, three minutes after half-time from Edmilson Fernandes, his first for the club.
Antonio Conte's team rallied later on with the introduction of Diego Costa and Eden Hazard, but it was not until the last touch of the ball for Chelsea that Gary Cahill scored.
To the Chelsea manager's credit he picked two academy boys in his team while Bilic made just two changes to the side that beat Sunderland at the weekend.
There has long been a resistance from Chelsea managers to dip into the academy in this competition and, while Conte may reflect that it cost him this cup tie, the reality was that his senior players like the returning John Terry, Willian and Oscar must shoulder much of the blame.
After the rush of victory over Manchester United, this showed that there will still be a great deal that must be done if Conte's three-man defensive line is to be a success.
Into the team came two of the academy boys, Ola Aina, the 20-year-old left-back from Southwark making his second senior start, and Nathaniel Chalobah, the 21-year-old, who was making his first start at this level.
Aina was obliged to play left wing-back in the new Conte team, with Terry adapting to this new way of life at Chelsea for the first time.
Snugly inserted between Cahill and David Luiz, Terry was largely protected from the general anxieties of conventional centre-halves dropped into a back three, although he will look back on the first West Ham goal with regret.
On that occasion he was simply beaten to the ball by a more aggressive, assertive leap from Kouyate, who was first to Mark Noble's cross from the left on 11 minutes and nodded it past the dive of Asmir Begovic. It is not often that Terry gets caught out by those kind of goals.
Bilic's team have been unbeaten - against Crystal Palace and Sunderland - since he adapted to a shape similar to Chelsea's, with three at the back and, for this encounter, Manuel Lanzini, Dimitri Payet and Michail Antonio deployed as a front three. Payet seemed to have a good shout for a penalty in the 15th minute when N'Golo Kante tried to nick the ball away from him in the area and brought him down.
On that occasion referee Craig Pawson allowed played to go on and there was a good chance for Antonio to finish but he wasted it. West Ham had the better chances in the first half, Antonio pinning Luiz out on the right and spinning past his man to cross for Lanzini, who flicked the ball wide. Pedro Obiang had a sweet low shot well saved by Begovic.
Kante was at the heart of the best that Chelsea managed but he was often out-manoeuvred by Noble, who had a fine game in the centre of the pitch. The best Chelsea move of the first half went from Chalobah to Oscar and into the path of Michy Batshuayi, who shot wide with a minute to play until half-time.
It may well have summed up Batshuayi's first half that, seconds after the whistle had gone for the break, he lashed one in frustration at Darren Randolph's goal and only succeeded in hitting the bar from close range.
It got a lot worse for Chelsea within three minutes of the restart when they made a mess of clearing a shot saved by Begovic and ended up conceding the second goal. It was Willian who failed to read Kante's clearance and allowed Aaron Cresswell to seize possession, square to Noble, who picked out Fernandes to drill home.
It prompted Conte to start pulling out the young ones and rolling out his big guns to try to retrieve the situation. The struggling Bashuayi was off before the hour with Costa on in his place and Hazard and Pedro followed soon after in the place of Chalobah and Aina.
It was not until 74 minutes that they created a notable chance between them, Costa taking the ball mid-flight and cutting one back intelligently for Willian, who snatched at it with his right foot.
Costa looked off the pace too, standing on the ball on one occasion - a moment that bizarrely convinced referee Pawson to book Winston Reid.
Free on goal late on, the Chelsea striker lashed one wide, and West Ham held firm until the very last Chelsea attack when Cahill slammed home a loose ball in the area. (© Daily Telegraph, London)