Peterborough 1 Albion 1 - West Brom win 4-3 on penalties - Report and pictures

Posh striker Lee Angol missed the deciding penalty after 210 minutes of football failed to separate the teams but Graham Westley's team dominated the majority of the game and can count themselves unlucky to bow out of the cup.

For 70 minutes the Baggies were humiliated by their lower-league counterparts, and resorted to kicking out at their best players, 18-year-old Martin Samuelsen - who also missed a penalty - and goalscorer Jon Taylor, who opened the scoring in the 55th minute.

Rescued by Fletcher's thunderbolt in the 71st minute, Albion took the game into extra-time where Craig Gardner had a shot cleared off the line and Berahino fluffed a free header on the final whistle.

But Peterborough created far more chances than the Baggies throughout the game.

Injuries to Craig Dawson, Jonny Evans and Chris Brunt forced Tony Pulis to play three at the back, but Gareth McAuley only lasted 18 minutes before the thigh injury he picked up at Newcastle flared up again.

Cristian Gamboa was handed his first appearance since September at right wingback and James McClean's willingness to shuttle up the left was tested on the other side.

Berahino hasn't started a Premier League game in more than three months, but he scored both of Albion's goals in the 2-2 draw at The Hawthorns and was given a rare start up front with Salomon Rondon.

Posh had their own problems with injuries and suspensions, but Graham Westley's attacking line-up got off to a bright start in front of a jumping crowd at London Road.

Martin Samuelsen is on loan from West Ham, and the teenager's mazy run in the sixth minute set up Harry Beautyman at the back post, but his shot was saved by a flying McClean block.

The Norwegian was flooding forward at every opportunity down the left, taking advantage of Gamboa's own desire to get forward.

He was moving the ball around well with Taylor - Peterborough's hero from the first match - and the former Shrewsbury midfielder had a couple of long-range sighters before Chris Forrester really tested Ben Foster with a swerving effort from 30 yards.

Buoyed by the bumper crowd, the League One side peppered the Baggies goal in the early stages, limiting Pulis's Premier League team to unsuccessful counter attacks and set pieces.

Craig Gardner's whipped free-kick on the half-hour mark just needed a touch on it, but none came and it was safely gathered by the bearded Ben Alnwick in the Peterborough goal.

Albion had stemmed the early tide though and not long after Berahino put Posh hearts in mouths, curling an effort inches wide from a Rondon knock-down.

Those members of the home crowd who had made the trip to The Hawthorns didn't need the warning, but it still served as a reminder.

As if that jolted Peterborough back into life, Taylor went on another direct run, breezing past James Chester, but there was no player in blue near his low dangerous cross along the six yard line.

McClean then had a shot blocked at the other end before Chester spurned the chance of the half from the resulting corner, somehow missing the target from four yards out at the back post.

The second half started exactly like the first, with Posh on top. Chester went some way to make up for his miss with a well-timed tackle on Shaquile Coulthirst in the box before Claudio Yacob finally picked up a booking for scything down the same striker on the edge of the area.

The free-kick was easily saved by Foster, but it didn't stop the onslaught, and in the 55th minute Taylor made the pressure count.

When McClean passed the ball backwards straight to Coulthirst's feet, the home crowd were screaming at their striker to get his head up.

Eventually he did, and found Taylor's run up the middle of the pitch. His finish wasn't as clinical as his brilliant volley at The Hawthorns, but it still bundled past Foster.

It was nothing more than Peterborough, or indeed Taylor, deserved.

The goal should have sparked the Premier League side into life, but even though Pulis threw on Stephane Sessegnon for Yacob, it was Westley's team who kept bombing forward and the League One side who controlled possession.

Samuelsen nutmegged McClean on the byline to the delight of the home crowd; all it needed was a second goal and the humiliation was complete.

But out of the blue the Baggies equalised, thanks to a belter from Darren Fletcher. In a rare foray up the other end of the pitch, McClean's cross was cleared towards the skipper and his half-volley from the edge of the area flew like a tracer bullet into the top left corner.

It was against the run of play but it rejuvenated the Albion team as the game became a frantic end-to-end feature in the final minutes.

Alnwick came for a long ball to Rondon with three minutes to go and when the ball fell to Berahino his long range effort was cleared off the line by Michael Bostwick and the game went into extra-time.

Weary legs opened the game up even more and Albion had the first sight of goal when McClean's cross got stuck on Bostwick before Gabriel Zakuani blocked Gardner's shot.

Samuelsen continued to torment the Baggies, beating two men before firing over, before it was Bostwick's turn to put his body on the line in front of a McClean shot.

Posh substitute Marcus Maddison tried an audacious chip over Foster which landed on the roof of the net before Gardner had a fiercely-struck volley from a corner heroically cleared off the line.

And right at the end Berahino got the chance he was waiting for, but somehow the striker put his free header at the back post wide and the teams went into penalties.

Fletcher missed his but Foster saved Samuelsen and Angol's penalties to send Albion into the fifth round where Reading await.

Peterborough (4-1-2-1-2): Alnwick (c), Zakuani, Baldwin, Taylor (Oztumer 105), Bostwick, Beautyman (Maddison 98), Fox, Forrester, Samuelsen, Angol, Coulthirst (Coulibaly 89). Unused subs: Henry, Ntlhe, Oztumer, Da Silva Lopes, Toffolo.

Albion (3-5-2): Foster, Gamboa, Olsson, McAuley (Pocognoli 18), Chester, McClean, Yacob (Sessegnon 62), Fletcher (c), Gardner, Berahino, Rondon. Unused subs: Myhill, Sessegnon, Anichebe, Ward, Roberts, Leko.