BARCELONA, Dec 6 (Reuters) - Real Madrid beat a desperate Barcelona side 2-1 on Saturday to claim their first league win at the Nou Camp in 20 years and aggravate the crisis engulfing their old rivals.

Real needed a modest amount of luck in a game that featured little in the way of good football, with both their goals from Roberto Carlos and Ronaldo being deflected past exposed keeper Victor Valdes.

They also had to withstand a bit of pressure at the end of the game, after Patrick Kluivert had pulled one back for the Catalans with a point-blank header from a corner seven minutes from time.

Real were well worth their victory, though, after succeeding in silencing the Nou camp crowd in what was a subdued Spanish derby compared to the mayhem of last year's meeting, when the referee was forced to lead the players from the field as missiles rained down from the crowd.

The result took Real back three points clear at the top of the table, and a whopping 13 points ahead of Barcelona with just 15 games played.

It also served to underline the fact that while Barcelona may be Real's greatest historical rivals, they are now hardly capable of troubling them on the field.

Barcelona came into the match on the back of a 5-1 defeat by Malaga in the league in midweek, a result that left them with just a point from three matches.

They picked up in the same abject form, as the players consistently misplaced their passes and pumped aimless balls forward for Kluivert to chase.

Coach Frank Rijkaard was unable to call on injured Brazilian playmaker Ronaldinho but he hardly did himself any favours with a bizarre series of selection decisions.

The Dutchman, under increasing pressure from the voracious Catalan sports media, opted to leave talented Argentine forward Javier Saviola on the bench and pack his side with out-of-form defensive midfielders.

Real could hardly believe their luck and Zinedine Zidane and David Beckham set about carving up the Barca side.

Beckham gave Valdes two nervous moments early on with a free kick from the left and a corner from the right, both just about dealt with by the keeper.

Barcelona looked content to snap at Real heels and hit on the counter-attack.

That tactic was failing but they still almost managed to take the lead on 36 minutes, as Xavi's free kick from a central position forced a fine save from Iker Casillas.

That finally roused the crowd but they were stunned into silence a minute later with the opening goal.

Beckham lobbed a long a pass forward to Zidane out near the left touchline and the Frenchman pulled the ball back for Roberto Carlos to hammer a shot in off Michael Reiziger.

Rijkaard reacted by bringing on wingers Ricardo Quaresma and Marc Overmars at halftime but there was little improvement and Real moved 2-0 ahead after 74 minutes.

Roberto Carlos was involved again, taking a pass from Figo in space and finding Ronaldo unmarked to smack in another deflected shot.

Kluivert's late goal restored some Barcelona pride but an equaliser rarely looked like coming and Real held on for a long overdue victory with some ease.

By Kevin Fylan