A Lionel Messi brace has put Barca in the driving seat after a heated affair at the Bernabeu
After a first-half devoid of any real scoring chances, drama ensued in the second session when the hosts were forced to play the final 30 minutes with ten men following a red card for Pepe.
Madrid’s mission was made all the harder when Lionel Messi expertly guided home Ibrahim Afellay’s cross in the 75th minute.
The Argentine star then scored a sensational goal when he waltzed past four Madrid players before sending the ball beyond Iker Casillas, sending the travelling support into raptures.
The opening exchanges took the same route as the previous Clasicos: neither side was able to settle early on, referee Wolfgang Stark being heavily involved from the beginning. Both sides looked to influence him as they attempted to gain a psychological hold on the German official.
Barcelona began to enjoy possession in their own half as the match developed, and came close to taking the lead through David Villa. The World Cup winner darted in-field from out wide and looked to strike the ball across Casillas, but his effort flashed past the far post.
At the other end Marcelo was eager to break forward, his tenacity soon winning Madrid what could have been a vital corner. The hosts hastily took the kick only for Angel di Maria to waste the promising crossing position to the frustration of his team-mates.
Casillas made the game's first stop when he got down low to save from Xavi. Messi had threaded a beautiful pass through to the Spanish international who took the shot first time, firing across Madrid’s goal with pace.
The Argentine repeated his contribution soon afterwards, this time finding Villa behind Real Madrid’s defence, but the striker’s touch deserted him as the men in white saw the danger clear with ease.
The officials became increasingly central to the tie close to half-time as tempers flared. Stark, ever the disciplinarian, had his work cut out to maintain control.
The half came to life in the final minutes when Cristiano Ronaldo smashed a long-range effort which Valdes could only parry. Mesut Ozil pounced on the rebound but shot straight at the 'keeper: his blushes were spared when the offside flag was raised.
As the players headed down the tunnel there was a ruckus between members of both teams, as an argument broke out, earning Barcelona’s second-choice goalkeeper Jose Pinto a red card.
The whistle had brought the most drama, adding fuel to the fire when the two sides re-emerged for the second-half.
The Blaugrana began the brighter of the two with Messi finding space between the midfield and defence. He shifted the ball to Pedro, who in turn found the Argentine with a delicate cross but Pepe recovered to clear the danger.
Barcelona took a quick free-kick as they looked to get Messi away and the striker took it beyond three Madrid players before Sergio Ramos body-checked the Argentine.
The challenge earned Ramos a yellow card, which will see the defender miss the return leg. Javier Mascherano levelled the caution count, soon after, when he went in recklessly on Pepe.
Pepe was then sent off for a high, studs-showing challenge on Dani Alves, leaving the Madrid bench to furiously protest the decision.
Jose Mourinho had contested the referee’s judgement and was sent to the stands after he sarcastically praised the fourth official after Pepe’s sending off.
Barcelona looked to take the imitative with the numerical advantage and Villa produced a fine save from Casillas as the Blaugrana began their onslaught on Madrid’s goal.
Soon after, the Spanish stopper could do nothing to prevent Barcelona from taking the lead. Lionel Messi expertly steered home his 10th Champions League goal of the season from close range after Ibrahim Afellay's swift cross from the right flank, and suddenly Barcelona were well and truly in pole position.
By Messi's standards, this was a mere tap-in - particularly in comparison to what was to follow. Five minutes from the end the little Argentine made history with one of the finest goals ever to be scored in European competition. Seizing the ball fully 30 yards from goal, Messi shrugged off the challenge of Lassana Diarra before playing a truly sumptuous ball - to himself! - past Raul Albiol.
By now he was in the box, but still had all his work ahead of him, for Marcelo and Sergio Ramos were closing in fast. As if they weren't there, Messi changed direction, cut slightly away from goal, then rolled a right-footed shot on the turn that had more than enough accuracy to leave Iker Casillas as helpless as his stunned teammates. A legendary solo goal, and one that surely propelled Barcelona to the Champions League final.
Pep Guardiola’s side walked off at the final whistle with a feeling of jubilation as they will welcome the Copa del Rey champions to the Camp Nou next Tuesday in the culmination of this Clasico Champions League tie.