The class of on-loan Arsenal striker Jay Simpson inspired West Brom to a 2-0 win over Peterborough and earn a place in the fourth round of the FA Cup.

Simpson's 18th-minute strike helped the Baggies to overcome a potentially tricky third-round replay at London Road.

United were dreaming of an upset after drawing 1-1 with Albion at The Hawthorns 10 days ago, but a second goal eight minutes before the interval from defender Paul Robinson crushed their hopes.

Albion should have taken the lead as early as the sixth minute when Leon Barnett headed a cross from Jonathan Greening inches wide of the far post.

But the League One side gave Albion a real scare moments later when Charlie Lee took advantage of some indecision in the Albion defence.

The midfielder burst into the penalty area and was ready to celebrate an opening goal but his clever chip fell the wrong side of Scott Carson's right-hand post.

But Simpson settled Albion's nerves with the opener - his first since joining the club from the Gunners.

Simpson, on-loan until the end of the season, collected a pass from Roman Bednar, swivelled on the edge of the penalty area and unleashed a rasping 20-yard shot into the corner of net.

Posh hit back immediately but George Boyd's shooting was not up to the same standard and his 25-yard shot was well held by Carson.

Albion's grip on the game forced Posh boss Darren Ferguson into the technical area in a bid to rally his side.

But they were being thoroughly outclassed by the Premier side who possessed two quality strikers in Bednar and Simpson.

Peterborough had to rely on goalkeeper Joe Lewis to prevent Bednar from increasing Albion's lead in the 33rd minute.

The striker weaved his way into the penalty area and was invited to shoot by Peterborough's back-pedalling defence. The Albion striker seized his opportunity but Lewis dived low to deny him.

But the second goal, which Albion had threatened since Simpson's opener, arrived in the 37th minute.

A superb curling cross from the right flank by Kim Do-Heon was met by an unmarked Robinson at the far post. The Albion defender sent a powerful downward header into the far corner with Lewis unable to get a hand to it.

But the visitors were fortunate moments later when a corner from Dean Keates caused confusion in the Peterborough defence and Carson misjudged his attempted punch.

The ball fell to Aaron McLean but referee Andy D'Urso adjudged that the Peterborough striker had fouled a defender in his bid to head the loose ball home.

Bednar then squandered a great chance to make it 3-0 in the 41st minute when he sent his shot over the crossbar from just 12 yards.

Albion continued to dominate after the interval and in the 52nd minute a cross from Greening was met by Bednar at the near post.

However, the Albion striker's diving header lacked direction and it flew wide of the target to the relief of Lewis.

Lewis then had to be at his best to deny Filipe Teixeira as Albion increased the tempo.

The England Under-21 goalkeeper did well to keep out Teixeira's angled drive by diving to his right.

Peterborough were finding it difficult to take the game to Albion but a cross from Tom Williams on the hour caused a moment's panic in the visiting defence before Carson grabbed the ball.

Seconds later a 20-yard shot from Lee was fumbled by Carson as Peterborough raised their game for the first time in the second half.

Posh, now playing with three in attack, continued their efforts to get back into the game and Boyd almost put McLean through on goal with a clever reverse pass into the penalty area.

In the 69th minute, Lee forced Carson to tip the ball over the crossbar with a deft header but Albion were happy to soak up the pressure.

It was the last real effort from Peterborough who could have fallen further behind had substitute Craig Beattie not been denied by the diving Lewis with three minutes left on the clock.

.