Only two teams have ever gone an entire La Liga season unbeaten - but they were both in the days when the 10-team division was 18 games long.

• 1929-30 (Athletic Bilbao) and 1931-32 (Real Madrid)

Barca are already on the longest unbeaten run in La Liga history - 41 games - last losing 2-0 at Malaga on 8 April 2017. You have to go back to September 2016, against Alaves, for the last time they lost at home in the league.

John McEnerney: A tad infantile from Real Madrid to not have a guard of honour. Barcelona didn’t do it for the Club World Cup because they weren’t in the competition, that was their reason - but it’s tradition (a load of codswallop in my opinion) in La Liga but I’m sure there is political motivation behind it! Iniesta’s last Clasico, some player! 2-1

Andy West
Spanish football writer at Nou Camp

Half an hour before kick-off and Real Madrid's players have been out warming up for about 10 minutes, but still no sign of Barca's players, who always have shorter warm-up than most. As I type those words, here they come, receiving a predictably big ovation from the home fans.

As the PA man announces the teams, for once it's not Lionel Messi's name to receive the biggest cheer. This time, ahead of his last Clasico, the warmest ovation is for Andres Iniesta.

Andy West
Spanish football writer at Nou Camp

A controversial side issue this week has been the subject of the 'pasillo', the guard of honour traditionally given to newly crowned champions by their next opponents before the game.

Zinedine Zidane has said Madrid will not give Barca that privilege because the Catalan club didn't honour them with a pasillo after they won the Club World Cup before December's Clasico.

Another possibility mooted was both teams lining up for Andres Iniesta ahead of his last Clasico, but Real wouldn't agree to that either.

So we can expect several renditions of one chant in particular from Barca fans, which translates as: Madrid, dear friends, salute the champions! (OK maybe they don't actually say dear friends.)

Image source, Andy West

Andres Iniesta still has two more home games after this but he's already started his long goodbye.

This is the first match at the Nou Camp since Spain's national treasure announced on 27 April that he was leaving at the end of the season.

Iniesta will make his 38th and final El Clasico appearance. If Iniesta does make it will he add to the three goals and six assists he has in this fixture?

Zinedine Zidane will hope not but the Real boss has paid tribute to the midfielder.

"He's a player we admire, not just any other player, and we all know how he is as a person," said Zidane. "We'll shake his hand, congratulate him and wish him luck for the future."

Image source, Rex Features

Matt Jones: Cheer up doc (19:10 BST)! Lots of class players on show, surely can’t be as bad as Everton/Southampton.

James Horncastle
European football writer on on BBC Euro Football Leagues Show

The only thing that can overshadow Barcelona's season is if Real Madrid win the Champions League.

I think bearing in mind everything they were going through in the summer when they lost Neymar and the fans were trying to get rid of the board, and given how badly they played in the Spanish Super Cup, this season has gone better than anyone could have expected really.

Listen to the show here.

Image source, Rex Features

Dr. Mark Ojuok: can't recall a more useless El Clasico, only thing riding on this is whether Real can end Barca's unbeaten run

Glad we didn't have Mark doing our marketing for this game!

Barcelona have already won the domestic double, La Liga and the Copa del Rey. They are yet to lose a league game under Ernesto Valverde - but imploded against Roma to go out of Europe.

Real Madrid are 15 points further down La Liga, crashed out of the Spanish Cup long ago, but they're in the Champions League final - where they face Liverpool on Saturday, 26 May in Kiev.

Andy West
Spanish football writer at Nou Camp

It will be interesting to see what kind of atmosphere there is for tonight's game.

There's always a special crackle in the air at El Clasico but tonight is a rare occasion where neither team has anything to play for (except Barca wanting to stay unbeaten all season) and both teams are in a good frame of mind with the hosts winning the league and the visitors through to the Champions League final.

But I'm sure when the game starts the relative irrelevance of the fixture will be forgotten - especially if Sergio Ramos puts in a couple of meaty tackles or the ref turns down a Barca free-kick or penalty appeal.

Image source, Andy West

Prince Gyimah: Alright. Attention directed to El Clasico. Enough of this fight for top four spot. We want to see how Barcelona keep their unbeaten record or whether it'll be derailed by Cristiano and his troops.

Aleel Oladipo: A guard of honour or not changes nada. It is a ridiculous practice anyway; has nothing to do with football. Whose idea was it to start with? It will feel awkward walking through a line of dudes clapping for me, if I am a player.

Who would you pick if you could choose anyone from Barcelona and Real Madrid?

Cristiano Ronaldo and Lionel Messi up front together? Toni Kroos or Andres Iniesta in midfield?

Have a go here.

Image source, .

Image source, .

The biggest surprise is Gareth Bale starting for Real Madrid.

They make three changes from the team who knocked out Bayern Munich on Tuesday - Nacho replaces Lucas Vazquez at right-back, Casemiro is in for Mateo Kovacic and Bale replaces Marco Asensio.

Barcelona make two switches from the side who beat Deportivo to win La Liga last weekend. Andres Iniesta starts in his final Clasico, replacing Ousmane Dembele, and Sergi Roberto takes the place of Nelson Semedo.

Image source, .

Image source, .

It wouldn't be El Clasico without a bit of pettiness.

Real Madrid have refused to give Barcelona, who clinched La Liga last weekend, a guard of honour onto the pitch today.

That's because Barcelona didn't do the same for them after Real won the Club World Cup in December.

This is the third time that El Clasico has come directly after one team has won the league, and only the sixth ever where one team have already been named champions.

What do you think, is this childish from Real - or fair enough? Tweet #bbcfootball or text 81111 (UK only for texts and please let us know your name).

Image source, Reuters

Four games from immortality.

That is how close Barcelona are to an unbeaten La Liga season - something nobody has achieved in the modern era.

Today is their final huge obstacle.

But what an obstacle.

It's Champions League finalists Real Madrid, in one of world football's great rivalries.

Welcome to live text coverage of El Clasico number 238.