"Iker Casillas came up to me and he said: 'Itu, I love you, but don't ever referee us again.'"

Eduardo Iturralde Gonzalez would have been tempted to take him up on that offer. The former referee laughs. "You know what we used to say the best thing about clasico weekend was? To get another game, any other game. That weekend, if you were doing another game, you knew you could make the biggest c--k-up of your life and no one would notice it; whatever you did, you wouldn't be in the papers, no one would be talking about you. Because the clasico eclipses everything."

A good time to bury bad news, you might say. Something like that, Iturralde agrees.

"If you get the clasico, the media attention is intense, the pressure's amazing. They're ringing you from everywhere. 'Hello, it's the University of Mexico student newspaper.' It's this lot, that lot, everyone's on the phone."

Of course, being a referee, you don't answer any of those calls and you never say a word. "Well, I did," Iturralde replies. "I was always a bit of a bit of a punk."

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He was also Spain's best referee for over a decade, spending 17 years at the top. And yes, he was a talker. He's also got his own band, by the way, so that punk thing is thing is not so far off. In that time, he took charge of three clasicos: 1999, 2005 and 2010. It might have been more. When referees were chosen by random draw (or supposedly so), he never got a chance. "'Curiously' enough," he says. And, yes, those speech marks are his. When it was chosen by the refereeing committee, with the best man selected for the job, he was chosen three times, but even then, there was no guarantee. He missed out on a Copa del Rey final clasico because Real Madrid vetoed him, leaving Alberto Undiano Mallenco to do the game instead. Madrid won 1-0; they were also within their rights, he says.

"There was a system where they would choose a three-man list [of referees] and the clubs could say 'no, not that one.' I suppose they didn't like the way I refereed."

No one does, in reality. No one is ever happy. And there was a headline once -- typical in Spain, where results are offered up as definitive proof of refereeing "bias" when what is really being shown in the bias of the media saying so -- that said: "Iturralde, good for Barcelona."

"Yeah," he scoffs, "that's like going to the Premier League now and saying: 'Referee so-and-so, good for Liverpool.' Bah, what you gonna do? Of course you're 'good for Barcelona' if you're there refereeing them in the Guardiola era."

That must make you angry though, right? "Nah, we're all so used to it."

Iturralde presided over three clasicos, all of them Barcelona wins. In 2010, he sent off Sergio Ramos for a nasty foul on Lionel Messi. David Ramos/Getty Images

When it comes to clasicos, Iturralde's games were good for Barcelona, it's true. He took charge of a 3-1 win, a 3-0 win and a 5-0 win. All about the referee, then. Not exactly tight results: Barca outscored Real 11-1 overall, which is a particularly historic scoreline in this fixture: it's the result of an (in)famous match in 1943 which is a whole history in itself, still disputed even now. Iturralde has been in the public eye, judged and criticised, his decisions pawed over, television footage stopped and started and analysed over and over. But whatever they see on the screen, whatever any of us do, it's just not the same, he says.

"I don't think you do enjoy it as such, no; you're too focused for that," he says. "When you get home, you see a load of things you didn't see during the game. But I tell you what: on the television there are loads and loads of things you don't see on the pitch. Above all, the speed is miles greater. It looks like slow motion on TV, but it's incredible how fast it is, the way they move. There's no television camera in the world that can transmit that or fully capture it. Seriously: the TV is not a true reflection of what's happening, which is one of the problems with the VAR, of course. Down there the speed is diabolical. Physically and mentally they are so, so fast."

It means that referees have to be, too, and never is the scrutiny more intense than on a weekend like this one, with the two teams separated by just two points at the top of the table with 13 games remaining.