ALAN SHEARER rescued Newcastle yet again just when it looked like plucky Peterborough were about to write another infamous chapter in the Magpies' chequered FA Cup history.

Skipper Shearer converted a disputed 83rd-minute penalty to restore his side's lead after Barry Fry's Second Division battlers had wiped out a 2-0 half-time deficit in yesterday's fourth-round tie at London Road.

Striker Leon McKenzie, who scored one of the goals that put Darlington out here in the last round, was harshly penalised for handball and Shearer was calm personified as he blasted home a precision spot-kick to notch his 18th FA Cup goal.

Six-times winners Newcastle last won the Cup in 1955 and since then they have suffered the humiliation of going out to non-league Bedford and Hereford.

It is 30 years since Ronnie Radford etched his name in Cup folklore with his wonder goal at Edgar Street.

And for a time yesterday, the Posh scented a repeat of their triumph over the Geordies at the third-round stage on Tyneside four decades ago.

But Shearer had other ideas and his 14th goal of the season allayed fears of a Cup shaker.

The most relieved man in the black-and-white ranks was surely centre-back Andy O'Brien, who was both hero and villain for Bobby Robson's side.

The Republic of Ireland defender handed Newcastle the lead in only the 14th minute and midfielder Jamie McClen, a late replacement for the injured Kieron Dyer, added a second two minutes from half-time.

But the Posh put the Magpies under the cosh after O'Brien had headed spectacularly into his own goal only four minutes into the second half.

And David Farrell levelled the scores in the 69th minute with a superb effort to leave Newcastle in a sweat.

Robson was adamant his side should have been awarded a penalty just after the break when Olivier Bernard was brought down by Tom Williams.

But Shearer made no mistake when his chance came and right-back Aaron Hughes settled the issue two minutes later, heading in at the back post on the end of substitute Wayne Quinn's left-wing centre.

Newcastle had been thrown into a midfield crisis when Dyer was a surprise absentee.

It meant McClen came in for his first start in domestic football for over two years to partner Clarence Acuna in a midfield bereft of broken-toe victim Gary Speed and Robert Lee, who was still struggling with a groin injury.

The game was only given the go-ahead an hour before kick-off after referee Neale Barry had carried out a pitch inspection.

Mercifully, the rain had stopped, but it was clear the cloying surface would cut up quickly.

The eager Craig Bellamy made light of the heavy conditions with a searing early break down the left, and Shearer should have scored soon afterwards when he mis-kicked from only eight yards.

But Peterborough responded when they forced a corner on the left and when the ball broke to skipper Andy Edwards, only the goal-line presence of Nolberto Solano prevented a goal.

Newcastle, however, settled any early nerves when O'Brien struck.

Robbie Elliott forged forward from left-back, finding Bernard in support, and the Frenchman wasted little time in hitting a low 25-yard drive which keeper Mark Tyler did well to touch wide.

But when Solano swung over the right-wing corner, Sylvain Distin knocked the ball down and O'Brien turned inside the six-yard box to force home.

Newcastle then had a scare when McKenzie made full use of his muscular physique to shake off the attentions of Distin and fire agonisingly wide of Shay Given's right-hand post.

Marc Joseph then played his side into trouble with a weak back-pass on the sticky surface and Tyler had to race from his goal to clear from the onrushing Bellamy.

Tom Williams was narrowly wide after letting fly from 30 yards before Given was forced to hack away at the feet of Andy Clarke as Peterborough desperately sought a way back into the tie.

Edwards, however, was a little too zealous with a crunching challenge on Bellamy which resulted in the game's first yellow card.

Acuna was next into Mr Barry's notebook for needlessly kicking the ball away after conceding a free-kick, and when Jimmy Bullard stepped up to take it, his curling effort wasn't far wide.

Newcastle established a flattering half-time lead when Solano played the ball inside, Bellamy attempted a back-heel and the ball ricocheted off a defender to break kindly for McClen who drilled in a cool finish.

But O'Brien's blunder - a thunderous header into the roof of the net from Marc Joseph's centre - made a game of it and the Posh rose to the occasion.

Neale Fenn missed a great chance to level when he knocked wide of an unguarded goal after Jimmy Bullard's cross had eluded Given.

But Farrell rocked Newcastle with a stunning breakaway goal, picking up Clarke's ball before cutting in from the right to bury a left-foot drive into the far corner of the net.

Given kept Newcastle alive in the 77th minute with a brilliant save after Fenn had tried to clip the ball past him from Farrell's measured through-ball.

Clarke then spotted Given off his line and was just wide with an audacious, looping effort.

But Newcastle regained the lead and the initiative when Solano centred and Shearer's header was blocked by Williams before the ball cannoned off the unfortunate McKenzie.

Read more about Newcastle FC here.