Ian Pearce's Jekyll and Hyde FA Cup afternoon was overshadowed by an amazing post-match brawl as Highbury passions exploded.

The Hammers and their fans were starting to celebrate a deserved draw when John Moncur picked up the ball and appeared to stick his head into Patrick Vieira.

The French midfielder - overshadowed by the battling Hammers during the game - responded by swinging a right hook which failed to make contact.

But that sparked real mayhem, with Frank Lampard storming in to push Vieira in the face and the Gunners star kicking out as Andy Impey came in before referee Mike Reed rushed over to restore order but not take any action.

At that it all broke up, the visitors restarting their parade of honour after an exciting game which was as noticeable for the performance of French keeper Bernard Lama as anything else.

From the first minute, when Lama saved from Dennis Bergkamp's free-kick, the Frenchman was a quality performer.

That gave the Hammers the platform for Pearce to crash home a shock opener, and for a while, as Harry Redknapp's men made light of a host of absences, it looked as if the East Enders would extend their 68-year FA Cup hoodoo over the Gunners.

But 18 minutes from the break Pearce made a fatal error to put Arsene Wenger's side back into the match, bringing down Martin Keown as the England man seized on a loose ball.

Bergkamp, back after injury, had no hesitation in steering his 19th goal of the season past Lama from the spot.

Yet much as Arsenal pushed forward, they could not find another way past the composed Frenchman, and if Eyal Berkovic had shown more composure on one occasion in each half they might already be celebrating a semi-final with Wolves.

Now they will have to claim it on home turf on Tuesday week, in the knowledge that Arsenal have gone through all three rounds to date away from Highbury, and hoping that tempers might have eased.

Post-War Cup history might have been on their side - West Ham had emerged triumphant from four pairings with their capital rivals since Arsenal's last victory in 1930 - but everything else seemed balanced against them.

Redknapp's men were without their first-choice front trio of John Hartson, Paul Kitson and Trevor Sinclair through suspension, injury and being cup-tied respectively, while David Unsworth was also missing.

But Rio Ferdinand was fit to play in a back three in front of Lama, with Berkovic playing off the energetic Samassi Abou.

Lama was playing his first FA Cup tie but could hardly have made a better start, flying to his left to turn the returning Dennis Bergkamp's 22-yard free-kick over after Steve Potts had crudely stopped Ray Parlour's run.

However, Lama only helped on Bergkamp's free-kick five minutes later, Tony Adams handing the Frenchman a let-off when he side-footed over.

But in the 13th minute the Hammers went down the other end to take the lead after Andy Impey's persistence had forced a corner off Nigel Winterburn.

Lampard's delivery was swinging away from goal, but Ferdinand stepped over the ball and with Arsenal wrong-footed, Pearce crashed a left-foot shot beyond Alex Manninger from 15 yards.

Pearce celebrated his first goal since moving south from Blackburn, and while at times they were stretched - with bookings for Potts and Steve Lomas - West Ham started to believe.

Indeed, after the excellent Ferdinand had nipped in to foil Vieira the visitors had a superb opportunity to double their advantage.

Stan Lazaridis sped past the lunging Keown and away down the right but Berkovic got the ball caught under his foot and the chance slipped away.

Three minutes later, Pearce gifted Arsenal the opportunity to level. The defender had initially done well to rob Parlour, but the ball rolled away from him and when Keown nipped in, Pearce's outstretched leg made contact.

Referee Mike Reed had no doubt, pointing to the spot, and Bergkamp converted with Lama helpless.

Lomas was lucky to escape a second yellow after handling in midfield and before the break Arsenal had the better of things.

Bergkamp crashed a shot against Lama's chest with Impey hacking the rebound away but on the break Moncur's first-timer brought a fine diving stop from Manninger, the Austrian reacting as the ball came through a crowd, and honours were deservedly even.

After the interval Lama denied Petit and Vieira failed to control eight yards out. But it was still on a knife-edge, Arsenal frustrated by the soaring Ferdinand, West Ham holding and looking to hit on the counter.

They were so close to doing just that on the hour when Pearce, again up from the back, nodded down Moncur's free-kick and Berkovic's shot went a fraction wide.

Nicolas Anelka, again a disappointment, was replaced by Christopher Wreh who saw a header clubbed away by Ferdinand before Lama saved from Petit.

The change sparked Arsenal, Keown running into the box, stopping and then going on again before falling under the weight of Ferdinand's challenge - but Mr Reed answering in the negative this time.

The final whistle saw that incredible spat, but the Hammers looked as if they believed the important job had been done.

Teams

Arsenal: Manninger, Dixon, Winterburn, Vieira, Adams, Anelka (Wreh 66), Bergkamp, Overmars, Keown, Parlour, Petit.

Subs Not Used: Garde, Upson, Lukic, Hughes.

Goals: Bergkamp 26 pen.

West Ham: Lama, Potts, Lomas, Ferdinand, Moncur, Lazaridis, Lampard, Pearce, Impey, Abou, Berkovic (Hodges 77).

Subs Not Used: Bishop, Sealey, Mean, Coyne.

Booked: Potts, Lomas, Lampard.

Goals: Pearce 12.

Att: 38,077

Ref: M D Reed (Birmingham).