Cristiano Ronaldo led Real Madrid to the Copa Del Rey final with a double that floored Barca.
But it was the sheer scale of Madrid’s win that was stunning.
Raphael Varane made it three midway through the second half and it seemed like the end of an era.
Jordi Alba’s late consolation for Barcelona did nothing to change the impression.
Sir Alex Ferguson was here to spy on Madrid ahead of their trip to Manchester United next week. Ronaldo’s supershow has sent a shiver down Fergie’s spine.
This triumph relieved the pressure on boss Jose Mourinho. It also plunged Barcelona into a full-blown crisis on a night of high drama at this vast venue.
Regardless of the result in Saturday’s Clasico in La Liga at the Bernabeu, Madrid will come to Old Trafford next Tuesday buzzing and full of belief.
Fergie sitting alongside No 2 Mike Phelan must have been stunned to see the ease with which Barcelona collapsed.
Madrid came here chasing the result after drawing 1-1 at the Bernabeu in the first leg – just like they have to do against United.
Led by the unstoppable Ronaldo, Mourinho’s men put on a show of tremendous organisation and discipline.
Yes it was controversial as Barcelona were denied a first-half penalty but the Catalans never took control.
This was probably Mourinho’s biggest win since he took charge at the Bernabeu three years ago given his team’s woeful season in La Liga where Barcelona have stormed 16 points clear of Madrid.
But this emphatic triumph proved they are far from finished and United’s task to get through next week will be a gigantic one.
Ronaldo put Madrid ahead on aggregate from the spot on 13 minutes after Gerard Pique brought him down in the box.
That opener sapped Barca’s confidence. They did not enjoy the occasion because they were not in control. For all they tried they could not actually find a consistent rhythm.
After 34 minutes Pedro was pushed by Xabi Alonso and fell in the box but the ref did not give the penalty.
The tie was decided 11 minutes into the restart as Ronaldo tapped home the second leaving Barca needing three goals to go through.
Varane’s 68th-minute header left the Nou Camp numb and Mourinho hugged the youngster and danced on the touchline in wild celebration.
Alba grabbed a late consolation for Barcelona but frankly the Catalans will take a long time to recover from this shock.
When his team needed it most Mourinho’s men delivered. Whether it proves a turning point in his Bernabeu tenure it remains to be seen.
But this astonishing result has given Madrid a great chance of a trophy.
The piece of silverware they really want is their 10th Champions League. Boosted by this performance Ronaldo & Co will certainly be hard to stop for United.
Who would bet against the Special One running down the touchline towards the corner flag in celebration at Old Trafford AGAIN next week?
Barcelona: Pinto, Alves, Puyol, Pique, Alba, Xavi (Thiago 77), Busquets, Fabregas (Villa 59), Pedro (Tello 71), Messi, Iniesta
Real Madrid: Lopez, Arbeloa, Varane, Ramos, Coentrao, Khedira, Alonso (Essien 83), Di Maria, Ozil (Pepe 73), Ronaldo, Higuain (Callejon 69)