Heidar Helguson's 10th goal of the season was enough to send Watford through to the fifth round of the FA Cup.

The First Division side were deserved winners against Premiership strugglers West Brom, who are now without a win in 11 away games.

Baggies keeper Russell Hoult had kept the away side in the match with a string of fine saves, including a penalty stop from Neil Cox.

Key moments

54 mins: Hoult saves Cox's penalty 80 mins: Helguson hits winner

But Hoult could do nothing about Helguson's 80th-minute winner following superb work from man-of-the-match Jermaine Pennant.

West Brom looked like a side short on confidence, despite enjoying the best of the opening spell.

Both Darren Moore and Jason Koumas came close for West Brom in the opening quarter-of-an-hour, but Alec Chamberlain stood firm in the Watford goal.

But the Hornets soon found their stride and began to dominate possession.

Hyde came close with a rasping drive from Neal Ardley's free-kick, forcing Hoult into a fine diving save.

Hoult was almost caught out minutes later when he hesitated in possession and was robbed by the nippy Tommy Smith, but referee Jeff Winter called a foul to spare his blushes.

With Pennant a constant menace for Watford, West Brom found it difficult to impose themselves.

Pennant's right-wing cross in the 31st minute found Helguson attacking the near post, but his header from four yards flashed just wide.

Watford began the second half in much the same vein and twice came close to breaking the deadlock in the space of a minute.

First Allan Nielsen crashed a close-range shot against the crossbar following Darren Moore's hacked clearance.

Then Tommy Smith was brought down in the area following a clumsy challenge from Moore.

Referee Jeff Winter pointed at the spot, but Neil Cox's penalty was well saved by Hoult.

To do as well as we did is beyond what we expected. It was a marvellous performance Ray Lewington

The visitors were rocking and worried manager Gary Megson threw on Larus Sigurdsson for captain Derek McInnes.

But Watford continued to attack and Nielsen, Vernazza and Smith all came close before Helgusson hit the winner with 10 minutes to go.

The inspirational Pennant was given room to run at the West Brom defence and he beat three players before picking out Helguson.

The Icelandic international was unmarked on the right, and he coolly slotted the ball past Hoult to send Watford through.

Watford: Chamberlain, Ardley (Mahon 89), Cox, Gayle, Robinson, Pennant, Vernazza, Hyde, Nielsen, Tommy Smith, Helguson (Noel-Williams 88).
Subs not used: Brown, McNamee, Lee.

West Brom: Hoult, Gregan, Moore (Adam Chambers 84), Gilchrist, Wallwork, Koumas, McInnes (Sigurdsson 58), Johnson, Clement, Roberts (Dobie 67), Dichio.
Subs not used: Udeze, Murphy.

Attendance: 16,975

Referee: J Winter (Cleveland).