IT may have taken six months but Watford are at last able to celebrate their first away win, and first back-to-back success of the campaign, after edging out West Ham United 1-0 at Upton Park to book their place in the fifth round of The FA Cup today (Saturday).

A game that was low on quality was decided just before the interval when Darius Henderson capitalised on a shocking error from keeper Roy Carroll, who decided to go walkabouts near the edge of his area, and Anthony McNamee hooked the ball into the empty net to knock last season's beaten finalists out of the competition.

Whether this result will have any bearing on the Premiership fixture between the two sides in a fortnight's time remains to be seen, but on this evidence Aidy Boothroyd's men look more up for the relegation battle facing both clubs. Jay DeMerit, Jordan Stewart, Damien Francis and Henderson were the stand-out performers, but all over the pitch the Hornets showed the stomach for the fight as the Hammers proceeded to waste a number of good chances without ever impressing.

With Gavin Mahon and Dan Shittu still sidelined, Boothroyd made just the one change to the team that recorded only its second Premiership victory at the expense of Blackburn. Anthony McNamee came in for the cup-tied Will Hoskins, which meant Hameur Bouazza moved up front alongside Henderson and new £500,000 signing Steve Kabba had to be content with a place on the bench. There was also a change among the substitute keepers. Richard Lee, who is set to play at Old Trafford next week as Ben Foster is ineligible, was carrying a slight niggle, so Alec Chamberlain came into the 16.

West Ham, meanwhile, made four adjustments to the line-up that was pegged back from 2-0 up to a 2-2 draw at Newcastle. Out went the cup-tied Calum Davenport, Marlon Harewood, who was suspended, the injured Anton Ferdinand and Yossi Benayoun and they were replaced by new signing Lucas Neill, Jonathan Spector, Shaun Newton and Bobby Zamora.

And it was two of the players Alan Curbishley bought into his team who so nearly combined to give the home side the lead in the third minute. The situation arose after Foster had tried to wait for the ball to roll back into his area to pick it up, but, under increasing pressure, he inadvertently conceded a corner, although that was only given after the linesman over-ruled referee Howard Webb. But the set-piece was eventually taken by Luis Boa Morte from the left and the unmarked Zamora sent a looping, angled header from around ten yards onto the top of the crossbar.

Both sides then proceeded to make a succession of mistakes during an end-to-end, but edgy, opening to the game, but in the 15th minute Watford thought they had taken the lead with their first meaningful attempt. McNamee clipped a nice measured ball in from the left, ex-Hammer Malky Mackay nodded it back across goal and Francis applied the decisive touch from close range, only to be flagged offside.

Nigel Quashie had the game's first legitimate on-target in the 20th minute with a 20-yard drive straight at Foster following a game of head tennis in the Hornets area after a free-kick for the home side, but soon after the Watford keeper had to make a better save at his near post to deny Newton after Boa Morte had burst through the middle. That led to two corners, the second of which ended with Stewart clearing from near Foster's left-hand post after Christian Dailly had headed Boa Morte's set-piece goalbound.

The home side then had a reasonable spell without creating anything of note, but ten minutes before the break the Hornets so nearly took the lead. A Stewart corner from the right was met by Henderson at the back post and his header back across goal looked to be going in until Carlton Cole got back on the line, just ahead of Francis, to put the ball behind.

West Ham though, were not far away from taking the lead themselves in the 39th minute when Cole turned away from Francis in a central position and tried a shot from 22 yards that curled just past Foster's left-hand upright.

But three minutes before the interval the Hornets were in front. Following a succession of mis-placed passes and unforced errors from both sides, Tommy Smith swung in a right-footed cross from the wing, Henderson beat Carroll, who bizarrely decided to come for the ball near the edge of his area, to the punch and the unmarked McNamee cleverly hooked the ball back over his left shoulder from around ten yards to make it 1-0.

Neill was then booked for a foul on Bouazza before Al Bangura pulled a 20-yard effort well wide of the target in injury-time, but the first period ended with a chorus of boos ringing round Upton Park as Watford took a one-goal advantage into the break.

The Hammers started the second period on the front foot, forcing a corner inside the opening minute, but they were forced into a change after 48 minutes when the injured Neill was replaced by John Pantsil.

Zamora had a good chance a minute later when he did well to squeeze in between Adrian Mariappa and DeMerit, but fired straight at Foster from the edge of the area. The Hammers striker had another decent opportunity in the 56th minute when he was picked out by Newton's cross from the right, but was unable to keep his header down.

There was then a moment of controversy in the 59th minute when Cole burst away from DeMerit down the left and, after appearing to run the ball out of play, he advanced into the area and looked to be clearly upended by a mistimed challenge from Mackay. However, much to Watford's relief, the referee not only failed to award the spot-kick but also booked the Hammers striker for diving.

But the home side kept the pressure on and, from a free-kick in the 63rd minute, the ball sat up nicely for Newton on the edge of the area but the midfielder dragged his shot wide of Foster's right-hand post.

Teddy Sheringham entered the fray for Newton two minutes later as the Hammers continued to press, although Watford had a chance when Smith broke down the right and his cross found Henderson in the middle, but the striker was unable to make decent enough contact and the effort went wide.

However, the Hornets survived a let-off in the 70th minute when Foster came for a Boa Morte corner from the right and claimed the ball, only to drop it, but fortunately his team-mates were able to clear the danger. Boothroyd then made his first change, bringing on Chris Powell for goalscorer McNamee and changing to a 4-5-1 formation.

Curbishley followed suit, replacing Boa Morte with Matthew Etherington with 13 minutes to go, but the home side still didn't look like getting back into the game despite having the majority of possession.

However, after Francis had been booked for a foul on Nigel Quashie after 84 minutes, it took some excellent defending to prevent West Ham from leveling. The free-kick from the right was pumped towards the far post where Spector headed back into the danger zone and, with Foster stranded, Stewart did very well to beat Sheringham to what would have been a routine finish.

Sheringham then tamely shot at Foster as the game entered three minutes of stoppage-time, but Watford safely negotiated these to ensure it will be their name in Monday's Fifth Round draw.

West Ham United: Carroll; Neill, Dailly, Spector, McCartney; Newton, Quashie, Reo-Coker, Boa Morte; Zamora, Cole. Substitutes: Pantsil for Neill after 48 mins; Sheringham for Newton after 65 mins; Etherington for Boa Morte after 77 mins; Mullins and Green not used.

Watford: Foster; Mariappa, DeMerit, Mackay, Stewart; Smith, Francis, Bangura, McNamee; Henderson, Bouazza. Substitutes: Powell for McNamee after 71 mins; Doyley, Kabba, Ashikodi and Chamberlain not used.

Bookings: Neill for a foul on Bouazza after 44 mins; Cole for diving after 59 mins; Francis for a foul on Quashie after 84 mins.

Attendance: 31,168.

Referee: Howard Webb.