West Ham sealed their place in the Championship play-off final by completing an emphatic semi-final victory over Cardiff.
The Hammers came into the second leg with a firm grip on the tie courtesy of a 2-0 win in Wales last week.
They strengthened this in the 15th minute when captain Kevin Nolan headed in from a Matt Taylor corner.
They made sure of the win when Ricardo Vaz Te fired in a superb drive with Nicky Maynard adding a late third.
Sam Allardyce's side remain on course to make amends for allowing automatic promotion to slip through their fingers. They are now just one game away from the Premier League, with either Birmingham or Blackpool representing the final hurdle at Wembley on Saturday, 19 May.
It will be West Ham's first appearance at the national stadium since the 1981 League Cup final.
For much of this season, United occupied a top-two spot and looked likely to earn an instant return to the Premier League, but Reading's late surge and Southampton's greater consistency throughout the campaign consigned the Hammers to an extended route to the top flight.
Three is the magic number
The club finishing immediately outside the top two has been the most successful in the play-offs in the last 20 years, gaining promotion seven times. West Ham are on course to add to this record.
While West Ham's away form is the best in the Championship this season - a fact they emphasized at Cardiff City Stadium last Thursday when Jack Collison's goals gave them an impressive first-leg win - their inconsistent home form is arguably the main reason they did not attain automatic elevation.
Four defeats and eight draws for the Hammers on their own turf was enough to give Cardiff hope of upsetting the odds by becoming the first team to overturn a two-goal first-leg play-off deficit at this level and thus keep alive dreams of a first top-flight season in 50 years.
However, this depended on them scoring the first goal and their failure to achieve this killed the tie.
The Bluebirds had made an encouraging start - and could have had a penalty had referee Mike Dean not been unsighted for a clumsy Winston Reid challenge that felled Kenny Miller in the box - but instead they suffered a terminal blow when Nolan nodded in after Carlton Cole's initial header from Taylor's corner had been blocked.
Malky Mackay's side never recovered as the home side capitalised on their position of superiority.
Gary O'Neil was close to extending West Ham's lead with a side-foot volley from 12 yards that struck the top of the bar, before Vaz Te did just that with a fiercely-struck shot that flew across City keeper David Marshall and into the far top-corner of the net.
The second half was a mere formality as a relaxed West Ham played out a comfortable 45 minutes, which they decorated right at the very end as substitute Maynard found space in the box to smash a shot past Marshall.
The Hammers' only concern was an injury to Collison, who was taken to hospital as a precaution for a dislocated shoulder.
The assistant referee flags for offside against Joe Mason. Free kick taken by Robert Green.
Don Cowie takes a shot. Robert Green makes a comfortable save.
Assist by Henri Lansbury.
89:09 Goal scored
Goal! - Nicky Maynard - West Ham 3 - 0 Cardiff Nicky Maynard fires in a goal from inside the penalty area to the top left corner of the goal. West Ham 3 (5)-(0) 0 Cardiff.
Filip Kiss concedes a free kick for a foul on Guy Demel. Free kick taken by James Tomkins.
Winston Reid takes the free kick.
Substitution Carlton Cole goes off and Nicky Maynard comes on.
Ricardo Vaz Te fouled by Darcy Blake, the ref awards a free kick.
Liam Lawrence has an effort at goal from outside the penalty area missing to the wide left of the goal.
Inswinging corner taken from the right by-line by Matthew Taylor, Ben Turner makes a clearance.
Substitution (Cardiff) makes a substitution, with Darcy Blake coming on for Kevin McNaughton.
Winston Reid takes a shot. Aron Gunnarsson gets a block in.
James Tomkins takes the free kick.
Booking Peter Whittingham goes into the book.
Gary O'Neil fouled by Peter Whittingham, the ref awards a free kick.
Matthew Taylor takes a shot. Save made by David Marshall.
Foul by Matthew Taylor on Joe Mason, free kick awarded. Peter Whittingham restarts play with the free kick.
Substitution (Cardiff) makes a substitution, with Filip Kiss coming on for Kenny Miller.
Substitution Stephen McPhail leaves the field to be replaced by Don Cowie.
Corner taken by Matthew Taylor from the right by-line played to the near post, Peter Whittingham makes a clearance. Short corner taken by Matthew Taylor from the right by-line.
Winston Reid challenges Kevin McNaughton unfairly and gives away a free kick. David Marshall restarts play with the free kick.
George McCartney fouled by Mark Hudson, the ref awards a free kick. Free kick taken by Ricardo Vaz Te.
Corner taken by Mark Noble from the left by-line to the near post, clearance by Peter Whittingham.
Substitution George McCartney comes on in place of Kevin Nolan.
Liam Lawrence takes the free kick.
Booking Winston Reid is booked.
Winston Reid concedes a free kick for a foul on Liam Lawrence.
Ricardo Vaz Te is caught offside. Indirect free kick taken by David Marshall.
Shot from just outside the area by Kenny Miller misses to the left of the target.
The offside flag is raised against Ricardo Vaz Te. Free kick taken by David Marshall.
The ball is sent over by Kevin McNaughton, comfortable save by Robert Green.
Unfair challenge on Andrew Taylor by Winston Reid results in a free kick. Direct free kick taken by Peter Whittingham.
A cross is delivered by Kevin Nolan, save by David Marshall.
Foul by Aron Gunnarsson on Henri Lansbury, free kick awarded. Free kick taken by Robert Green.
Matthew Taylor concedes a free kick for a foul on Joe Mason. Free kick crossed left-footed by Peter Whittingham from right wing, clearance made by Matthew Taylor. Corner from the right by-line taken by Peter Whittingham, clearance by Matthew Taylor.
The referee gives a free kick against Henri Lansbury for handball. David Marshall restarts play with the free kick.
Unfair challenge on Winston Reid by Joe Mason results in a free kick. Robert Green takes the direct free kick.
Matthew Taylor restarts play with the free kick.
Booking Mark Hudson receives a caution.
Free kick awarded for a foul by Mark Hudson on Ricardo Vaz Te.
Free kick taken by Peter Whittingham.
Substitution Jack Collison leaves the field to be replaced by Henri Lansbury.
Liam Lawrence fouled by Mark Noble, the ref awards a free kick.
The offside flag is raised against Gary O'Neil. David Marshall takes the free kick.
Andrew Taylor fouled by Kevin Nolan, the ref awards a free kick. David Marshall takes the direct free kick.
The second half begins.
45:00 +2:06 Half time
Half Time The whistle is blown to end the first half.
Winston Reid challenges Liam Lawrence unfairly and gives away a free kick. Liam Lawrence takes the direct free kick.
Carlton Cole produces a header from inside the area that goes over the bar.
Winston Reid challenges Aron Gunnarsson unfairly and gives away a free kick. Strike on goal comes in from Peter Whittingham from the free kick.
Guy Demel provided the assist for the goal.
39:46 Goal scored
Goal! - Ricardo Vaz Te - West Ham 2 - 0 Cardiff Ricardo Vaz Te scores a goal from inside the penalty area to the top left corner of the goal. West Ham 2 (4)-(0) 0 Cardiff.
The assistant referee signals for offside against Kenny Miller. Robert Green takes the indirect free kick.
Corner taken by Liam Lawrence from the left by-line played to the near post, free kick awarded for a foul by Aron Gunnarsson on Robert Green. Robert Green takes the free kick.
Gary O'Neil takes a shot. Save made by David Marshall. Corner taken by Mark Noble, save by David Marshall.
Mark Noble challenges Peter Whittingham unfairly and gives away a free kick. Peter Whittingham restarts play with the free kick.
Inswinging corner taken left-footed by Matthew Taylor.
Kevin McNaughton fouled by Kevin Nolan, the ref awards a free kick. David Marshall restarts play with the free kick.
Booking Kenny Miller goes into the referee's book for dissent.
The referee blows for offside against Joe Mason. Robert Green takes the free kick.
Effort from outside the penalty box by Ricardo Vaz Te goes wide right of the target.
Unfair challenge on Stephen McPhail by Kevin Nolan results in a free kick. Peter Whittingham crosses the ball from the free kick left-footed from right wing.
Gary O'Neil takes a shot.
14:18 Goal scored
Goal! - Kevin Nolan - West Ham 1 - 0 Cardiff Kevin Nolan scores a headed goal from close in. West Ham 1 (3)-(0) 0 Cardiff.
Corner taken right-footed by Matthew Taylor from the right by-line,
Free kick awarded for a foul by Carlton Cole on Mark Hudson. Kevin McNaughton restarts play with the free kick.
Unfair challenge on Kevin McNaughton by Carlton Cole results in a free kick. David Marshall takes the free kick.
Mark Hudson takes a shot. Save made by Robert Green.
Free kick awarded for an unfair challenge on Winston Reid by Kenny Miller. Robert Green restarts play with the free kick.
The assistant referee flags for offside against Aron Gunnarsson. Robert Green takes the indirect free kick.
Effort on goal by Carlton Cole from just inside the penalty area goes harmlessly over the target.
Free kick awarded for a foul by Aron Gunnarsson on Mark Noble. Robert Green takes the direct free kick.
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