Yep, he's firing now! After Lewis misses 122 on the bull, Van Gerwen takes out a 107 finish on double 18.

The world number one has one foot in the final.

What a way to respond from Michael van Gerwen.

The Dutchman powers in a fourth 180 followed by a 140 before taking out 81 on double 12 for an 11-darter.

That's a statement of intent if you ever saw one.

Remember, the second Premier League semi-final between Phil Taylor and Gary Anderson follows immediately after this match.

The final, a best-of-21-legs affair, is expected to begin at about 21:15 BST - possibly a little later, depending on how quickly these last-four ties get wrapped up.

Image source, Rex Features

Lewis is back in this now! After the Stoke thrower fires in a maximum it's another leg of missed doubles as Lewis can't find double top before Van Gerwen wires double 16.

However, Lewis steps in for double five in the corner and he's back to within two legs.

The players leave the stage for a mini-break.

Is this game about to turn around? Lewis wins back-to-back legs by finishing on double 18.

You'd say no, but Van Gerwen has gone off the boil for the last couple of legs.

Image source, Getty Images

That was the best record of any player in the group stage of this year's Premier League.

Michael van Gerwen was closely followed by Phil Taylor (47%), Gary Anderson and Adrian Lewis (both 40%).

The Dutchman hasn't been too sharp on his doubles in the semi-final thus far, but he's still doing enough to close in on a place in the final.

My goodness he needed that. After Van Gerwen misses the bull for a 164 finish, and then fails to take out 25, Lewis steps in to take out 83 on double nine.

Now he needs to find another gear badly.

Yep, this is becoming a rout now. Adrian Lewis misses 98 on double top and Van Gerwen steps in to take out the same double.

This guy just makes it look so simple. Van Gerwen starts the leg with 180 and 140 before leaving himself double eight which he takes out first time.

Lewis is not looking at the races so far.

Already evidence of some fancy dress on show in London... it's a night at the darts - what do you expect?

Image source, Rex Features

Image source, Rex Features

Michael van Gerwen is beginning to pull away already.

He fires in double eight to move three legs clear.

There's plenty of double trouble on show at the moment. Michael van Gerwen misses double nine for a 123 finish but eventually finishes on double one.

Lewis also missed two darts at a double eight and it's another break of throw.

Lewis breaks straight back! Both players hit maximums, but Lewis takes out double 20 to reduce the arrears to one.

Image source, Rex Features

This is already looking ominous for Adrian Lewis.

Lewis misses a dart at double 16 and a dart at double eight and Van Gerwen steps in to take out tops at the fourth attempt.

Early break of throw for the world number one.

Easy as you like for the best player in the world. Van Gerwen hits 140, 134 and 140 before taking out 87 on the bull.

Lewis hits a 180, but it makes no difference.

Image source, Getty Images

This is how Michael van Gerwen and Adrian Lewis shape up...

Gary Smee will be taking you through the first of this evening's semi-finals.

It's Van Gerwen, the world number one, throwing first...

Next up, world number one Michael van Gerwen. "Ohhh Michael van Gerwen" rings around the O2.

The atmosphere is red hot and we're a couple of minutes away from the first dart being thrown.

Who's your money on?

So here we go, the waiting is over. The O2 Arena in London is packed to the rafters and the crowd expectant.

Adrian Lewis walks on first to chants of "duh duh duh, Adrian Lewis". It never gets old!

Don't forget, let us know your favourite walk-ons using #bbcdarts on Twitter.

Image source, Getty Images

It seems fairly ridiculous when you're talking about a back-to-back world champion being an "outsider" tonight - but that's how the bookies see Adrian Lewis' chances.

However, the 31-year-old Stoke-on-Trent thrower is confident heading into his semi-final match against world number one Michael van Gerwen.

"I've always said I'm a better player when it's knockout and that's what this is now, and I don't fear anybody," he said.

"My scoring hasn't been fantastic, certainly over the last few weeks, but I've finished well. As long as I combine the two then I've got a great chance."

Michael van Gerwen is the Premier League's form player having gone unbeaten in the competition since losing to James Wade on the opening night.

And the Dutchman is now ready to win his first Premier League title since 2013.

Image source, Rex Features

"I'm desperate to win because I haven't won it for the last two years," he said.

"I feel fantastic but I need to show it on Thursday. You can't afford any mistakes, so I'll be 100% focused on the title."