There's something about Real Betis. Whether it is the man who took his dad to every game despite him being dead, carrying a milk carton of ashes to the stadium and perching it on his usual seat; the fan who turned up with a box tied to his head that doubled as a 'cage' for a green budgie that flew back and forth; or the giant loaf of bread baked into a Betis shield and held aloft like a great big doughy trophy, there's something about them. Something special. Some will wince when they read that, rolling their eyes and muttering: "not again". Others will dismiss the populist portrayal as folklore, not fact. But even those who shun the cliches that have been imposed upon and embraced by the club on the Guadalquivir – and there are plenty of them – would claim that Betis are different.

They'd be right too. Few fans are noisier, more numerous, more loyal or, simply, more fun than Betis's. When it comes to béticos, there are lots of them, they get everywhere and you can always hear them coming. They're the country's sixth most popular club* and economic migration from Andalucía has spread them all over Spain. At 40,000, only four First Division clubs have more season ticket holders and for sheer enjoyment, few trips rival Heliópolis. For many, Betis are defined by a now famous phrase that binds earthy pride, identity and location. It first appeared in the early 50s when they were relegated to the Third Division, and became a ubiquitous slogan. Always written phonetically, incorrectly, to reflect its supporters' voice, it runs: ¡Viva er Betis manquepierda! Long live Betis, even if they lose!

Today, more than ever. Today it really will be ¡Viva Betis!, even if they lose. Betis haven't even played yet in week six but it makes no difference. On Monday night, they travel to Getafe – and although it's the graveyard shift, some will travel there – and they could get hammered 17-0 but still not care. The reason is simple: Betis can get hammered 17-0 and still lead La Liga. They're clear at the top for the first time in 10 years; when the final whistle goes and week six officially ends just before 11 o'clock, they'll have been top for two consecutive jornadas for the first time since 1934-35. And 1934-35 ended with Betis being led to Santander by an Irishman named Patrick O'Connell and returning as champions – for the only time in their history.

This is the joint best start in Betis's history, alongside 1963-64 when they finished third. They are already a point ahead of Barcelona and two ahead of Real Madrid, clubs with budgets more than 10 times the size of theirs and a summer shopping list 25 times as big. And they have a game in hand. Win against Getafe, who are second bottom, and Betis will have a four-point lead at the top. Four wins out of four makes Betis one of only four teams, alongside Barcelona, Sevilla and, amazingly, Levante, who have not been beaten this season. After Manchester United's draw at Stoke this weekend, it also makes them the only team in a major European league with a 100% record.

Not bad for a club that has just come up from the Second Division – one whose aim was, said AS at the start of the season, "survival"; a club whose aim was, said Marca at the same stage, "not to go down". Even the coach Pepe Mel said this week that the best thing isn't the one-point lead that Betis have at the top but the 11-point lead they have over the bottom. After all, it is not just that Betis have come up from the Second Division, it is that "survival" could just as easily be applied literally.

These have been difficult times for Betis. Relegated in 2008-09, that alone does not tell their tale. Their owner and president Manuel Ruiz de Lopera – the fraudster whose bizarre and often comic behaviour hid his true perniciousness – had his shares embargoed by a judge while a criminal case was brought against him. The charge? Robbing from the club that, many years before, he had saved, creating for himself the position of president in perpetuity and modestly renaming the stadium the Ruiz de Lopera. Battles continued over the shares – and may yet continue. There have been protest marches, ownership challenges and judicial intervention. And, faced with an institutional crisis and a debt of €84m, Betis were forced into administration.

As it turned out, it was a step in the right direction. Administration, which brings no sporting penalty in Spain, provided stability – first under the former player and club legend Rafa Gordillo, whose emotional significance united supporters, shareholders and players, bringing peace at last, and now under the new president Miguel Guillén. But it also imposed restrictions. Each year, Betis are obliged to pay off €10m from their €47m debt and every transfer has to be ratified by a board that is led by administrators whose concerns are – at least in theory – purely economic.

Last year, there was no money for signings; this summer, Betis have spent only €1.6m on players. For that, they brought in nine footballers. Theirs in not the smallest budget in the division – Rayo, Racing, Sporting, Osasuna and Levante have all spent less – but there are only two players in the squad that cost anything: Javier Matilla, who joined from Villarreal for €1.4m (and so far is not even playing), and Antonio Amaya from Wigan for €200,000. Others, such as Francisco Chica, unwanted and released by Espanyol, have come on loan or free transfers, but the key players so far were already here – playing in the Second Division. Only three of the squad played First Division football last year.

Everyone wanted Betis back – there is something wrong about a First Division without them – but few expected them to come back like this. It's one thing to be in the primera, quite another to be on the top of it. "It's lovely to see so many people so happy," Roque Santa Cruz says, "no one expected us to be top at this stage." Or indeed at any stage. Yet, while they won't stay there, (not least because they are conceding goals too), for now at least you couldn't say Betis don't deserve it. Or that they have got there by the classic newcomers' trick of kicking, diving and cheating. Asked if the results were deceptive, not a real indication of their performances, Mel replied: "If you're living in Alaska, they might seem false, but anyone who has actually watched us knows they are not."

The coach had a point. Betis, who were denied the chance to mark their return with a Seville derby on the opening day because of the players' strike, have played the teams in 11th, 15th, 16th and 18th and on Monday they play the side 19th. But they have played well. They have committed fewer fouls than any other team and scored more goals than anyone bar Madrid and Barcelona. Their midfield three is made up of Beñat Etxeberria, Iriney and Salva Sevilla. And much as Beñat was signed from the Second Division B side Conquense and joined Betis's B team, Sevilla from Salamanca, and Iriney from Almería two seasons ago, where he rarely played, they make a neat, precise and creative trio. Jefferson Montero is fast, Jonathan Pereira is creative and quick, and up front they have Roque Santa Cruz with two already, and Rubén Castro who has the same amount and scored 27 last season.

And that's the thing: maybe we shouldn't be quite so surprised, even if Achille Emaná in the summer was sold to service the debt. Mel is a charismatic, talkative and unrelentingly positive coach who has been able to build a position of power within the sporting structure at Betis, jealously guarding his patch and succeeding in a way that no coach could ever do under Lopera. He has been bold in bringing players through the youth system – José Cañas, Juan Calahorro, Casto and Beñat were all brought from the B team, while the exciting 16-year-old Alvaro Vadillo became the youngest Betis player ever to make his First Division debut on the opening day – and he has been just as bold in his approach. This is a team built to attack.

Last season, Betis were easily the Second Division's best side, spending two thirds of the season top and scoring 85 goals. As if to sound a warning, in the Copa del Rey they beat three First Division teams as well: Getafe, Zaragoza and a certain FC Barcelona. Now, Betis are beating Barcelona again. By Tuesday they could be four points clear of the Catalans, five ahead of Real Madrid. Or they could not. Truth be told, they don't even really care. Against Getafe, more than ever, Betis's fans will enjoy themselves. Even if they lose.

Talking points

• Had Sevilla been in Alaska last week? The home page of their website automatically only shows the teams immediately round them; by happy coincidence that meant cutting off the league table at second place and not having to see their biggest rivals on the top. It was just a technological quirk but it had tongues wagging for a while.

• "You don't describe Leo Messi," Pep Guardiola said, "you watch him." It was a good job, too – the superlatives ran out long ago. But, hey, let's try and find some anyway. The Argentinian was just ridiculously good – again – as Barcelona destroyed Atlético Madrid 5-0 at the Camp Nou. Messi got another hat-trick, his third against Atlético. For the first goal, he took a throw in, got the ball back and then seemed to be pretending not to be interested, before suddenly swivelling his hip, bursting past two defenders and curling it into the near post. For the second he did what he does so often, running diagonally across the area away from players, George Best-like, before cutting the ball back into the other corner. And for the third he played a neat one-two and thumped it between the on-loan Chelsea goalkeeper Thibaud Courtois's legs. "When you come here, either Barcelona put out their kids or you have to produce the game of the century," Gregorio Manzano said with a sigh.

• It was one of those weekends when you suspected Leo and Cristiano had spent the morning on the phone again. So, Cris, three this week? Sure, three. OK, then. Not that it started well for Madrid; they were a goal down after 12 seconds against Rayo Vallecano. And after the week Madrid had endured, that prompted whistles and more than a few nervy looks. That was the bad news; the good news was that Rayo opened up, continued attacking, and offered Madrid the chance to play with space – and with space there is no one like them. Ronaldo hit a hat-trick; Madrid hit six. Six which flattered them a bit but, still, six, for goodness' sake. And although two of them were penalties, they were a hell of a pair of penalties – the second a Panenka, the first an absolute rocket that actually hit the roof of the net from the inside, while still rising. Still, the best goal was a leaping, outside of the foot volley from Rafael Varane that made him the youngest foreign goalscorer in the club's history.

• Juan Carlos Garrido, the Villarreal manager said he thought opponents Athletic Bilbao were "very good". Few agreed.

• Sevilla-Valencia should have been brilliant. Instead, it was ugly. Aritz Aduriz got himself sent off after falling into a dastardly trap laid by Fernando Navarro and Emir Spahic. It all started with a challenge from Aduriz on Navarro which wasn't especially bad, but which Navarro – one of La Liga's most practiced masters of the dark arts – made a meal of. A moment later, Navarro and Spahic surrounded Aduriz who was caught saying: "What a pair of twats, you like to wind me up, don't you?" To which they might as well have said "yes" and smirked in his face. Spahic sneakily trod on Aduriz's toe. Aduriz trod on Spahic's toe back. Spahic collapsed to the floor, while Navarro hopped up and down squealing for the red card. The card was promptly delivered and everyone forgot about Kanouté's neat goal. "That was the world's best acting," Valencia president Manuel Llorente moaned. "I would ask the Valencia president," replied Sevilla's José María del Nido, "whether if I trod on him in the street he would fall over." We never got to find out.

• Levante – yes, Levante – have now won three in a row and are in a Champions League place. Two penalties gave them a lead against Espanyol and Bakero added a brilliant third. Amazing.

• Mallorca won. Laudrup's safe. For now.

Results: Sevilla 1-0 Valencia, Athletic Bilbao 1-1 Villarreal, Real Madrid 6-2 Rayo Vallecano, Barcelona 5-0 Atlético, Mallorca 2-1 Real Sociedad, Levante 3-1 Espanyol, Granada 1-1 Osasuna, Sporting Gijon 0-0 Racing Santander, Zaragoza 0-0 Málaga. Monday night: Getafe v Betis

*The other five, since you ask, are Real Madrid (32.8%), Barcelona (25.7%), Valencia (5.3%), Athletic Bilbao (5.1%), and Atlético Madrid (4.3%). And the four with bigger season ticket sales: Madrid, Barcelona and Valencia.

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