And unsurprisingly at a corner a couple of minutes later the referee now gives a free-kick against Dunk for very little.

Dunk turns around and looks aghast. I've no idea what Chris Kavanagh thinks he has seen there.

Shane Duffy holds his arms out wide after a tussle at a Brighton corner. Lewis Dunk chases after the referee Chris Kavanagh appealing for a penalty kick.

Replays show Millwall's Jake Cooper had a strong hold of Duffy's arm as he went to head the ball.

You've seen them given. There's no VAR today, remember.

Jermaine Jenas
Former Tottenham midfielder on BBC One

There are a few signs that the game can open up and become a little bit more entertaining. In the last 15 to 20 minutes, it has calmed right down.

Image source, PA

The game opens up for a brief moment and the Millwall fans roar their players forward as Gregory has space to run in to.

The striker is shut out though and then Shane Ferguson gives away a foul.

It's very scrappy.

Brighton have upped it in the last five minutes. Chris Hughton repeated barking on the touchline has worked.

Anthony Knockaert now shoots from the right edge of the box but the ball is sliced wide of the far top corner with his left foot.

You could see what he was trying.

Image source, Reuters

Brighton left-back Bernardo is the first player to be booked for a late challenge on Mahlon Romeo. It's going to be a tough afternoon for him now.

That's a chance! Probably the best one we've seen. Anthony Knockaert cuts back and swings a lovely cross into the middle.

Beram Kayal drifts off the back of his marker and has a free header but makes poor contact. It's easily saved.

Image source, Getty Images

Another crossfield ball goes out of play off a Brighton boot. This time Davy Propper is the man at fault.

More cheers from the home fans.

You wouldn't know the visitors were the Premier League side.

Jermaine Jenas
Former Tottenham midfielder on BBC One

Brighton lack a bit of pace, they're a bit lethargic. Who has the pace to get between the lines? I'm not really seeing it.

Not this time. Brighton get this corner clear at the third or fourth attempt. There's still a fair bit of encouragement for the Millwall players. They've had the better of the opening half an hour.

Steve Sidwell
Brighton coach and former midfielder on BBC Radio 5 live

Millwall have not just gone long in the opening 30 minutes. They have mixed it up and played some neat football. It's been a very good start by Millwall.

Image source, AFP

Oooo. Nice effort. Millwall pump it long into the box and striker Lee Gregory is first to the second ball. He tries to flick the ball over his shoulder and into the far corner but the ball lands on the roof of the net.

Moments later more good pressure results in a Millwall corner...

Brighton have their first serious shot on goal. A cross is cleared to the edge of the box to Beram Kayal but as the visitor's striker shots on goal he slips. That takes some of the power away from the shot and Martin is able to save.

Image source, Getty Images

Steve Sidwell
Brighton coach and former midfielder on BBC Radio 5 live

It's a proper cup tie. Every time a Brighton player gets the ball a blues shirt is straight in his face. Millwall are harassing their opponents.

Image source, Getty Images

Good goalkeeping from Millwall's David Martin. At a corner Brighton put Glenn Murray in front of him and Dale Stephens behind to try and limit the goalkeeper's ability to come and claim the ball. The delivery comes in right under the crossbar but Martin gets a good punch on the ball.

Jermaine Jenas
Former Tottenham midfielder on BBC One

Neil Harris will be the happier of the two managers. Brighton need to get the ball down more, knock it around, get some runners in behind.

Image source, AFP

Is The Den the most popular ground for flat caps in the country? They're everywhere.

Brighton's Alireza Jahanbakhsh tries to ping one out to Knockaert again on the opposite flank but gets it badly wrong. The ball flies out for a goal kick and the Millwall fans unsurprisingly sarcastically cheer.

Chirs Hughton lets Jahanbakhsh know what he thought of the pass. He gives the forward a right telling off.

Image source, PA

Jermaine Jenas
Former Tottenham midfielder on BBC One

There's no doubt that Ferguson is good going forward, but every now and then he is going to get caught out. But he doesn't look like he's playing out of position because his attitude has been excellent.

Here's Anthony Knockaert on the ball for the first time. He beats Shane Ferguson who slides in rashly and the Brighton winger is then charging into the box. Unlike last week when he put it in the top corner from a similar position against Crystal Palace, Knockaert can't quite get the ball under control. Millwall clear.