The visitors began the game strongly and almost forced the opening goal when Jonas Olsson headed wide of his own post from an Adam Lallana cross.

James Ward-Prowse's cross was then spilled by Ben Foster, but West Brom managed to clear.

The Baggies began to press forward and James Morrison tested Artur Boruc with a speculative effort that was pushed behind by the Saints goalkeeper.

A scramble in the Albion box almost produced the opening goal for the Saints, but Lambert was unable to get his shot away.

Lallana had the ball in the net after 33 minutes when he nodded home Lambert's header, but the Saints captain was called offside.

Southampton continued to push forward and Luke Shaw had a long-range shot tipped wide by Foster.

The start of the second 45 minutes followed the same pattern as the first, with Mauricio Pochettino's men having most of the ball and the better chances.

Lambert had a header gathered by Foster, before Jay Rodriguez cracked the crossbar, but play had already been stopped for a foul by Lallana.

Shane Long could have scored for the Baggies but his back-hell rolled wide of Boruc's post.

The Saints had debutant Calum Chambers to thank for keeping out James Morrison with a crucial block from Billy Jones's cross.

Long, who was beginning to come into the game, then combined with Nicolas Anelka on the edge of the box, but the latter's shot was easily saved by Boruc.

Matej Vydra and Markus Rosenberg were introduced for Long and Anelka respectively, but it was Saints who broke the deadlock with a penalty in the 89th minute.

Mulumbu tripped Luke Shaw and Lambert stepped up to continue his fantastic week and put Southampton in the lead.

The Baggies almost responded immediately but Boruc somehow saved Jones's header.