Blades midfielder Greg Halford rose highest on the hour-mark to head home Kyle Walker's superb cross and settle a nerve-jangling second leg 1-0 in the Blades' favour.

It was no more than Blackwell's side deserved at a raucous Bramall Lane and they now stand one game away from a return to the top flight two years after their controversial relegation.

The Carlos Tevez affair threatened to rip the heart and soul out of the club in 2007, but the anger and sense of injustice were momentarily forgotten tonight at the final whistle when ecstatic Blades fans in a crowd of 26,354 spilled on to the pitch.

Blackwell said: "A lot of people have contacted the club in the last few days and there have been a lot of emails, because they feel it would right a wrong.

"It's been sorted out, but it's still festering among football people who feel things weren't right.

"I don't think that sits well with people in English football and most of the fair-minded supporters, so if we can get that right it would go a long way to lancing the boil totally."

There had been little to separate the two sides in Friday night's 1-1 first-leg draw at Deepdale, but this time the Blades seized the initiative with a high-octane display that Preston manager Alan Irvine conceded his side could not live with.

Blackwell added: "We were magnificent. Every aspect of our play was first class, the way we moved the ball, the tempo, the passion, the commitment, the organisation.

"It was a terrific team performance and I thought we thoroughly deserved victory."

Blackwell saluted match-winner Halford, who is on a season-long loan from Sunderland.

The gangly midfielder took a blow to the ribs and a boot in the groin in the first half and injured his Achilles before making way for Leigh Bromby late in the second half.

Blackwell added: "He's decent on the ball, he's a terrific athlete.

"Greg doesn't know how far he could go and he has to be reminded constantly that when he sits back on his laurels it's not good enough, but he's really knuckled down here."

Preston counterpart Irvine was "bitterly disappointed".

The Lancashire club have now failed to get through the play-offs on four occasions since winning promotion from League One in 2000.

But Irvine, who helped North End fend off relegation following his appointment in November 2007, was quick to point out the progress his side had made this season.

He was also gracious in defeat, saying: "We wanted to go the next step and then the one after that, so we're all clearly very disappointed.

"I can't speak for previous play-offs and it wasn't down to luck this time in any case.

"Sheffield United were better than us in both games and deserved to go through overall.

"But we've made great progress and the lads can be very proud and I told them that.

"As a result of their hard work they've managed to progress to a level nobody expected."