A poor header by the normally-reliable Antonio Valencia gives the ball to Brighton's Jurgen Locadia. His well-struck shot from the edge of the penalty area is arrowing into the top corner, that is until Sergio Romero makes a stunning save to push it away one-handed.

Brighton's best moment of the match. An alarm for the hosts.

Michael: Strange substitution. Shaw has a great first half.

Jack: Luke Shaw has a major hand in the goal... gets subbed. Jose’s logic is unbelievable.

Anon: Anyone a bit worried about Luke Shaw? Seems to have gone backwards again?

Image source, PA

Nimble feet from the big man Romelu Lukaku. But he does the hard part, of keeping the ball when three Brighton players are snapping at his heels, and is then let down by the straightforward pass as he tries to release the over-lapping Ashley Young but gets too much power on the pass and the chance goes.

Stephen Warnock
Ex-Liverpool defender at Old Trafford

Image source, AFP/Getty Images

I wonder if Luke Shaw going off was due to injury or tactical? With the way Brighton play there is the opportunity for full backs to get forward.

With Ashley Young being a former winger he naturally gets further up the pitch, which can create some two versus one situations out wide. Could be a long night for Brighton if they can do that.

Simon Stone
BBC Sport at Old Trafford

It is nowhere near the scale of recent cup matches at the Emirates Stadium but there are plenty of empty seats dotted around Old Trafford tonight.

Not sure whether it is due to the Saturday night kick-off, the style of football, Tuesday's result or a combination of all three.

A chance for Brighton. It comes from a well-worked move and it falls to Pascal Gross outside the area, but he pulls it just wide of the post.

He then has another attempt a few sections later but it pings off the legs of Nemanja Matic. Jurgen Locadia also draws a save out of Sergio Romero. Better from Brighton.

Image source, PA

Lukaku rolls the ball backwards into the path of the lively Anthony Martial, but Solly March gets a foot in to stop the Frenchman.

The cameras pick out Sir Alex Ferguson, who like everyone at Old Trafford, looks very cold. He is wrapped in a big, thick scarf and seems to not be overly excited.

Ashley Young is straight into the action, his low cross coming off Ezequiel Schelotto for a home corner. Juan Mata whips it in, but Shane Duffy powerfully heads it to the safety of the touchline.

Image source, AFP/Getty Images

Ricky: Well we are winning but again it’s slow and all in front of the opposition, this isn’t good to watch.

David: There is still a lot to come from this side, I believe.

Stephen Warnock
Ex-Liverpool defender at Old Trafford

Image source, Reuters

It will be difficult for Brighton. They came with a gameplan to keep it tight and nick a goal, maybe even take it to penalties. Now they have to attack United, maybe get something form a set piece.

They have been positive at times, it's just that killer instinct in the box they've lacked. Hopefully we can see more of them in the second half.

And we are under way in the second half.

Image source, Reuters

Former Brighton striker Warren Aspinall on BBC Sussex: "We're still in the game. They'll be disappointed with the goal - you can't switch off for one minute against these top stars. "They just need a bit of belief in the final third and move the ball a bit quicker."

A change for Manchester United to tell you about and Ashley Young is the man to come on.

Luke Shaw makes way. It is a big few months for Young, who is back in the England squad for the games against Netherlands and Italy later this month.

Can the 32-year-old get himself into Gareth Southgate's World Cup squad?

OK, so not the most thrilling 45 minutes. But the second half will be much, much better. Goals, goals, goals. Trust me.

Matt: OK....1-0 up but I can't help thinking United need to seriously up their game if we progress...just look at those already through.

PJ: Decent first half performance by the lads and an important goal for us before the break. Let's pick up the tempo and get some more goals in the second half to boost the moral again!

Stephen Warnock
Ex-Liverpool defender at Old Trafford

It can be hard in conditions like this, tough for players to get going and to get warm. When you make slide tackles the ground is cold.

But those are the conditions and you have got to get on with it. Also the pitch will play slower and the snow will hold up the ball.

It's fair to say it hasn't been the best of halves at Old Trafford but United do go into the break with the lead.

You can watch how Romelu Lukaku put United ahead below.

Stephen Warnock
Ex-Liverpool defender at Old Trafford

It’s been effective football. An improvement on what we have seen in the last few weeks but you still expect more.

Perhaps when Brighton tire in the second half and Marcus Rashford maybe Alexis Sanchez come on, the game might open up even more.

Image source, Getty Images

Just one shot on target apiece in that first 45 minutes.

Time for Brighton to bring on Glenn Murray at the break?

Image source, .

Stephen Warnock
Ex-Liverpool defender at Old Trafford

You look at Brighton and Solly March has been a bright spark for them, gotten 1-1 with Luke Shaw a couple of times.

They have been dangerous but the one thing Man United still do really well under Mourinho is they get back into shape quickly and make things difficult.