Jordi Alba crosses from the left and Sergi Roberto's legs are about a yard too short to turn the ball home. Barca might end up getting a goal back.

Real Madrid have had 56% of the possession so far, I'm surprised it's not been more.

Real Madrid make a change in central midfield as Casemiro, who started the first leg, replaces Mateo Kovacic.

Real Madrid don't feel like they're missing Cristiano Ronaldo too much...

Killian Everard: If Guardiola was the ultimate Barce coach, Zidane is the same for Real. Manages all the egos and plays such attractive footy

Helles Mammut: Real Madrid have taken their foot off the gas considerably, not more than a training session now with a 5-1 lead...

Marcus Kimber: Back-to-back champions league wins puts Zidane among the very best ever.

Sammiiee!!: Zidane has worked with the very best managers now he's one of the very best

Barca are starting to look a bit better now in fairness, Nelson Semedo crosses to Luis Suarez, but his glancing header is saved by Keylor Navas.

A chance suddenly opens up for Barcelona striker Luis Suarez but Raphael Varane blocks his shot.

Then Lionel Messi rolls the ball out left, but there's a Neymar shaped hole there and it goes out for a goal kick.

Andrew Ogley: Amazing to see how the balance of power has well & truly shifted in La Liga. Real Madrid stunning. Barcelona look ordinary.

Marcus Kimber: Write Barcelona off at your own peril...

Karim Benzema almost adds a second after going past Javier Mascherano, but his shot is saved by the arms of keeper Marc-Andre ter Stegen.

Barca were enjoying a decent spell there, but then suddenly Karim Benzema controls a ball dead, Javier Mascherano gets it out for a throw-in, and it's Real back in possession.

It's almost a consolation (surely we're not even considering a comeback) for Barcelona, Lionel Messi skips past a couple of defenders and his shot from a bit of an angle hits the crossbar.

Barcelona make a change in defence as Gerard Pique comes off for right-back Nelson Semedo, who makes his debut after his summer move from Benfica. Another formation reshuffle perhaps.

Ayush Shrestha: Barca need 4 gls. They scored four against PSG in the second half with Neymar. Can they do it without him?

No...

Luis Suarez gets behind the Real Madrid defence for once, and his cross or shot, whatever it was is held by Keylor Navas with no Barca players gambling.

Seth Gogo Egoeh: People are beginning to realise the great work Zidane is doing. He should be up there among the best managers in the world.

I was going to ask this, should we actually be crediting Zinedine as one of the modern managerial greats?

What response will we see from Barcelona? The second half is under way.

Good news for bosses and managers in Madrid, this game can no longer go to extra time. Which means it'll be over before 1am local time. Also good news for Salford-based live text commentators, who are getting a bit sleepy.

First Marco Asensio made it 1-0 (4-1 on aggregate) with a rocket...

Image source, Reuters

And then Karim Benzema span Samuel Umtiti to smash home a second

Image source, Reuters

John Bennett
BBC World Service

Luis Enrique got out at the right time!

Barcelona off to sign some players at half-time...

This is so bad that you can imagine Ousmane Dembele handing in a transfer request - and he's not even there yet.

Stu Thompson: Barca don't control the midfield anymore. Neymar helped cover the cracks but have struggled to dominate since Xavi left.

Chris Painter: Are Barce on some kind of cultural exchange with Crystal Palace? It's the only thing that explains this performance

Doctor Joker: Zidane has put new life into Madrid. They play such frightening football.

Good tweet, but I'm not sure I'd go to a GP called Dr Joker...