Simon Stone
BBC Sport at the London Stadium

Antonio Conte sacrificed Nemanja Matic to get Tiemoue Bakayoko last summer.

So far, it doesn't look a great deal.

Whilst Matic has adapted well to life at Old Trafford and, arguably, been the inspiration behind Manchester United's improvement this season, Bakayoko has been a shadow of the player who excelled at Monaco last season.

He has time on his side but, in the here and now, it is a step backwards on last season.

Three rows of West Ham fans get out of their seats to gesture at Eden Hazard as he waits for a ball to return from the top of the stands.

West Ham then break quickly. There's a chance for a one-on-one but by the time the ball is released for Marko Arnautovic he has strayed offside.

Brilliant from Chelsea now. N'Golo Kante into Eden Hazard, who flicks delightfully with his backheel to speed up a move on the edge of the box that was West Ham in a flutter.

They manage to hold firm and force the Blues back to Pedro, who shoots wide on the edge of the box.

Image source, Reuters

Pat Nevin
Ex-Chelsea winger at the London Stadium for 5 live Sport

Image source, Reuters

I expect to see a much more lively attitude from every single player in the Chelsea team...

Not sure how long West Ham will let Michail Antonio take these long throws - that's twice he's only just reached the penalty box.

A change indeed for Chelsea. Winger Pedro is on for midfielder Tiemoue Bakayoko.

Back under way.

Trevor Hawkes: Masuaku having a great game - I reckon there's enough footage from the first half today to put together a show-boating DVD and get it out for Christmas.

Steve Harwood: To those saying you are seeing the best of Arnautovic, it does happen! Just one or twice a season. Very inconsistent player hence why he's never made it at the top level.

Sam Kier: Bakayoko a passenger, Zappacosta a bit brainless on the ball... not good enough if you want to challenge for the league!

Pat Nevin
Ex-Chelsea winger at the London Stadium for 5 live Sport

Chelsea weren't up for it, they didn't start quickly, and West Ham have simply been the better team. I have been so impressed with the Hammers' defending.

However, I am sure Antonio Conte will do something very different with Chelsea in the second half - different tactics or different personnel.

Simon Stone
BBC Sport at the London Stadium

For those who say this stadium is incapable of generating atmosphere, the last couple of minutes of the first-half proved it can.

West Ham greeting a neat passing move with a series of 'Olés' and Anthony Taylor's half-time whistle brought thunderous applause.

Give the fans something to cheer - and they will.

Noel Fitzpatrick:Need to stretch the Hammers on the wings, tailor made for Pedro and Willian.

Ben, London: Very confused by Conte starting with Bakayoko again!? He hasn't been good enough, liability defensively.

Tom, London: How does Bakayoko keep getting selected ahead of Willian?

Oof. Here's grim reading for West Ham fans.

No team has lost more Premier League games after leading at half-time.

But the Hammers are not alone - they're level on 22 with Tottenham.

Pat Nevin
Ex-Chelsea winger at the London Stadium for 5 live Sport

West Ham finished that half strongly. They enjoyed a number of corners in a row and when they broke they found all sots of space. Whereas when Chelsea break they have had very little space because the hosts are defending so well.

West Ham's fans will know their squad is full of decent players that are too good to be in their current dire league position. There's enough quality for West Ham to easily stay up.

Changes for Chelsea?

Image source, Reuters

Arthur Masuaku with a stepover. Another one playing with real confidence. The Hammers ping the ball around in front of the Chelsea backline and the home fans are cheering every pass.

Manuel Lanzini then breaks through to space, but his fired pass out wide is cut out.

TWO minutes added time.

W'ere seeing the best of Marko Arnautovic though - finally. A lovely touch to link up with Manuel Lanzini in midfield and West Ham could actually end this half in search of another.

Their latest corner is whipped in by Lanzini and Alvaro Morata connects to clear at the near post.

On the sidelines, Antonio Conte scratches his stubbly chin. We haven't seen Chelsea at their best yet.

West Ham are straight back to their defensive posts - all lined up on the edge of the box and just beyond. They want to protect this lead and nothing more.

With under five to go to the break, you do not want to concede now.

Pat Nevin
Ex-Chelsea winger at the London Stadium for 5 live Sport

Much, much better play from Chelsea. Oddly, though, this is exactly what David Moyes would have been expecting - he'd have known there would be periods of play where Chelsea would see all of the ball.

So the Hammers have various controlling tactics, and so far they are executing them brilliantly.

Another unconvincing intervention from a keeper - Thibaut Courtois this time.

He comes to deal with a long ball over the top and inexplicably kicks out for a corner instead of a throw.

That's cleared but West Ham are back for a second bite. Manuel Lanzini launches in and Courtois gathers. A let off.

Image source, PA