A thrill-a-minute second half ended in bedlam as Pompey, leading 1-0 with Matt Taylor's 30th-minute strike, following Edwin van der Sar's blunder, saw Taylor's overhit pass to Lomana Lualua in the 88th minute turned past the Dutch goalkeeper by Ferdinand's intervention.

And although John O'Shea's tap-in after Pompey keeper David James spilled a soft Ole Gunner Solskjaer shot gave United hope, the giant James regained hero status - after his mistake cost him a record 142nd Premiership shut-out - by saving substitute Alan Smith's shot right at the death.

It is the third time in four Premiership seasons that United have come a cropper at Fratton Park but they could not deny it was a fully deserved success for Harry Redknapp's side.

On paper it looked a no contest with Pompey having won just one of their previous 11 league games and United arriving on the back of seven successive Premiership wins.

But Redknapp's side had won two of their previous three encounters with the Red Devils at Fratton Park, although last season United collected a 3-1 success among a run of five successive wins against the south coast team.

United decided on a circumspect start against a Pompey team clearly up for the challenge.

Sean Davis twice fouled Paul Scholes in the first five minutes and the red-haired United forward was also caught late by Taylor.

Pompey's early probes brought a half chance, with Kanu leaping to apply a twisting header to Taylor's good ball into the box, but van der Sar held on comfortably under the crossbar.

Djimi Traore, a late selection after Sol Campbell pulled out of the Portsmouth team despite taking part in the warm-up, briefly had to go off for treatment after a tackle with Fletcher before Ronaldo bounced a United free-kick from 30 yards tamely past a post.

The Portuguese was similarly off target a minute later after a mesmerising run from Wayne Rooney's run but it was a sign of United warming up.

On 16 minutes, Ronaldo darted between Linvoy Primus and Dejan Stefanovic but could not make contact with a dropping ball which ran clear towards Rooney ten yards from goal.

Primus was quickly up and there first, stretching to toe the ball away before Rooney fell over his outstretched leg. The England star inquired about a penalty but referee Mark Clattenburg saw that the Pompey defender had played the ball first.

That was bad enough for United who expect to get their spot-kicks but worse was to follow on the half-hour.

Kieran Richardson could not clear a ball that bounced up from Traore's throw-in on the left and Benjani jumped in to drill an early drive that van der Sar could only stand up and parry.

Taylor was quicker than Ferdinand to the rebound and tucked it neatly past the veteran goalkeeper.

Pompey fans particularly enjoyed that as they had been jeering van der Sar for a theatrical fall after Taylor - back in the team at the expense of last week's scorer Niko Kranjcar - gently tugged his sleeve.

Then they gave Ronaldo the treatment after the Portuguese fell easily from a Sean Davis challenge. Richardson could only sky the ball over the bar after gathering Ronaldo's free-kick.

Michael Carrick almost put United back on level terms immediately after Taylor's strike, his low shot drifting just wide but then James - hunting his clean-sheets record - blocked Darren Fletcher's shot with his legs after Rooney played the midfielder through.

Primus, outstanding at the back for Pompey and defying his 33 years, even found time to go up for a corner and head Gary O'Neil's delivery just over the bar.

And just before the start of first-half stoppage time Taylor turned the ball past van der Sar again only to see it hacked clear.

Ferguson was concerned enough to send on Ryan Giggs for Richardson at the start f the second half, which meant 10 of the 11 who faced Roma last Tuesday in the Champions League, were on parade.

Solskjaer completed the full set when replacing Fletcher 15 minutes later and he seemed to inspire United to a purple patch that threatened to turn the game around.

James excelled, pushing away Ronaldo's flick from a corner and Lauren backed him up to block Wes Brown's follow-up.

It was all hands to the Pompey pump as Rooney set up Giggs to force James into another save and then the Welsh international fired in a cracker to send James leaping for an immaculate tip-over.

When Rooney skated clear on 69 minutes, Primus timed his recovery tackle to perfection once again and the England striker's volatile protest to the referee cut no ice. Once more television evidence seemed to prove the defender's timing was dead right to take the ball first.

Ronaldo scuffed a chance wide as United's frustration grew but Pompey were still in it as an attacking force, Kanu's long-ranger stinging van der Sar's palms before the keeper made an excellent save, diving to push away Davis's goalbound shot.

Ferdinand inadvertently sealed it with his own-goal two minutes from the end.

James' error handed O'Shea what was no more than a consolation thanks to the former England keeper's late save from Smith.