Russell Martin's side moved a step closer to promotion thanks to Will Smallbone's second-half opener and two late goals from Adam Armstrong in the semi-final second leg at raucous St Mary's.

Cedric Kipre's header in the final seconds was no consolation for out-classed Albion.

Bidding to end their one-year exile from the Premier League after last season's relegation, Southampton will head to Wembley on May 26 for what is regarded as world football's richest game, given the wealth on offer in the top tier.

After a goalless first leg at the Hawthorns on Sunday, Southampton were deserved winners, with their confident performance showing why they finished fourth in the table, 12 points clear of fifth-placed Albion.

British prime minister Rishi Sunak, a noted Southampton fan, cheered from the stands as Martin's men responded to their manager's pre-match plea to "attack the game until you can't run any more".

The only blemish for Southampton was a post-match pitch invasion that turned ugly when Saints fans confronted their Albion rivals, with punches briefly traded before police restored order.

"In the first half, we were good but a little bit tense. In the second half, I thought we were incredible. I feel we got what we deserved," Martin said.

"We had a brilliant night but it's all leading to the big one. If we can play with the same courage and intensity as we did tonight, we can give ourselves a chance."

West Brom boss Carlos Corberan added: "We didn't show our best level. I had confidence in our team but it is more about the pain that we have after this defeat."

- Armstrong double -

Leeds had crushed Norwich 4-0 at Elland Road in the second leg of the other semi-final on Thursday, with Canaries boss David Wagner sacked on Friday.

That ruthless dismissal underlined the desperation of Championship clubs to strike it rich in the Premier League.

The Saints are no different but they rose to the occasion with a commanding display after surviving an early scare.

West Brom's aerial prowess caused problems when Grady Diangana glanced a header wide from Alex Mowatt's cross.

Southampton quickly took control and David Brooks' close-range effort cannoned off the post from Armstrong's cross.

Playing with Jed Wallace as their lone forward, Albion used a five-man defence in a bid to subdue the Saints.

Southampton keeper Alex McCarthy had to scramble back to push Tom Fellows' cross over the bar just before it dipped into the net.

But Martin's team were well on top and Brooks' drive from 25 yards was repelled by Alex Palmer.

Southampton's dominance was finally rewarded in the 49th minute thanks to a moment of magic from Smallbone.

Picked out by Brooks' pass after Diangana carelessly surrendered possession, Smallbone unleashed a ferocious strike from just inside the area that fizzed past Palmer via the inside of the post.

McCarthy preserved Southampton's lead with an instinctive tip-over from Darnell Furlong's blast.

And Armstrong netted the killer second in the 78th minute when he drilled a fine low finish into the far corner from 12 yards.

Eight minutes later, the Saints were ready to march on Wembley after Armstrong made it 23 league goals this season with a clinical penalty after Fellows fouled Ryan Manning.