As the rain pelted down and thunder reverberated around Vicarage Road, a storm was brewing for Arsenal - and the Gunners only just survived a second-half onslaught by Watford to keep their Champions' League chances firmly on track.

Despite having seized a 3-0 half-time lead with a superb display by Thierry Henry, who scored twice and set up another for Ray Parlour, the Gunners should have sealed victory.

Watford certainly do not lack spirit though and they battled back into contention with goals from Heidar Helguson and Micah Hyde.

The main controversy, however, was reserved for the final seconds of the game and it was perhaps hardly surprising that referee Rob Harris and midfielder Patrick Vieira should have at the centre of it.

Furious Watford players claimed that Vieira had head-butted Helguson yet Harris, who had obviously seen the incident, responded by showing the Frenchman a yellow card.

It seemed at best a curious decision, given that Vieira must either have made contact or not made contact, yet given Harris's track record, anything is possible.

He was the official suspended for his part in the substitution fiasco in the FA Cup tie between Sunderland and Tranmere, while he also incurred the wrath of both Tottenham and Aston Villa a couple of weeks ago.

The incident at the heart of his latest decision will surely be viewed and reviewed on TV replays, yet, whatever the outcome, the longer-term repercussions of the game at Vicarage Road will still be felt by both sides.

That Arsenal boss Arsene Wenger should believe Ruud van Nistelrooy was hopelessly over-priced at £19million after his capture of Henry for half that price only last summer is hardly surprising.

For the 22-year-old striker was yet again in inspired form at Vicarage Road as, virtually single-handedly, he all but condemned Watford to the First Division and continued the Gunners' push towards a Champions' League place.

The French international may have taken time to find his feet in the Premiership, especially in adapting to a central striking role, but he has now scored 23 times.

Indeed, he has scored in each of his last seven starts, clipping home the 18th-minute opener at Vicarage Road with considerable finesse and then embarking on a memorable solo run before curling home the third.

Had it not been for him, however, Arsenal would surely have stumbled as most of the rest of the side appeared to be in a strangely lethargic mood following their midweek exertions.

For amid the second-half thunder and lighting, Watford showed considerable determination and heart as they struck back and showed up the increasingly shaky Arsenal defence.

With the inspirational Tony Adams again absent through injury, Watford could easily have secured a draw and were furious at not being awarded a penalty after less than two minutes when referee Harris once more courted controversy.

Harris turned down strong penalty claims when Helguson tangled with David Seaman after an awful back-pass by Gilles Grimandi.

Watford were still bubbling with determination though and after Henry had shot wide for the visitors, winger Tommy Smith then burst clear through the centre only to be denied by a superb reaction save by Seaman.

Arsenal's defenders were in some disarray but Watford's season has been plagued by their ability to press the self-destruct button.

And it took just one visionary pass by Emmanuel Petit to put Henry clear at the other end and the Frenchman calmly slid his shot underneath the body of keeper Alec Chamberlain.

Hyde was unfortunate to strike the post yet Arsenal counter-attacked again to devastating effect, with Henry turning creator to send Parlour scampering through the middle.

Despite an attempted tackle by Paul Robinson, the winger went round the static figure of Chamberlain to slot the ball just inside the far post.

With just seconds to go before the interval, Henry went on a sublime run himself as he jinked his way around four defenders before striking a wonderful curling effort inside the upright.

Arsenal's pace continued to cause Watford problems, with Marc Overmars shooting against the post but Watford's spirit could never be faulted and the home side pulled themselves back into the game in an amazing two-minute spell.

On 58 minutes, a deflected free-kick by Neil Cox spun into the air and Helguson stole in unmarked at the far post to beat Seaman to the ball and to score from the tightest of angles.

Then, within 60 seconds of the restart, Watford had scored again - and this time England keeper Seaman was badly at fault.

Martin Keown's weak defensive header fell at the feet of Hyde, who hit a half-volley which hardly flew into the net but instead bounced just in front of Seaman and over his diving body.

As the rain poured down, Arsenal were forced to battle to hold onto their three points, although Henry did hit the corner of post and bar with one breakaway effort and then Vieira appeared to clash with Helguson.

Tempers were still frayed after the final whistle, as Vieira appeared to refuse to shake Helguson's hand, appearing to indicate that the Frenchman thought the striker had been play-acting.

However, the Gunners had still held on and Watford now need a mathematical miracle to stay up.

They lack nothing in spirit but the coup de grace will surely be applied by next week's visitors to Vicarage Road: Manchester United.

Teams

Watford: Chamberlain, Ward, Page, Robinson, Cox, Palmer, Hyde, Perpetuini (R. Johnson 86), Smith, Smart (Gudmundsson 72), Helguson.

Subs Not Used: Day, Gibbs, Bonnot.

Booked: Helguson, Page.

Goals: Helguson 58, Hyde 60.

Arsenal: Seaman, Luzhny, Keown, Winterburn, Parlour, Vieira, Petit, Grimandi, Bergkamp, Henry, Overmars (Silvinho 63).

Subs Not Used: Manninger, Dixon, Malz, Gray.

Booked: Bergkamp, Keown, Vieira.

Goals: Henry 18, Parlour 43, Henry 45.

Att: 19,670

Ref: R Harris (Oxford).