Va-Va, the theory goes, has lost his Voom. For country, that is, certainly not for club, as purring English Premiership-watchers will confirm.

He hasn't scored in nine of his last 10 internationals, having got 11 goals in his previous 13, even failing to get the better of the Faroe Islands' defence last month. And all the while he's been positively sublime, utterly peerless for Arsenal. As Arsene Wenger put it, "I have run out of superlatives."

He was, by his own club standards, mediocre in France's woeful attempt to defend their title at the 2002 World Cup, where he was sent off in his second game, and, again, at the European Championship in the summer, scoring in just one of his six games in the two tournaments.

The French, aghast at their team's recent failures, are beginning to despair of his form. Where, they ask, is the Thierry Henry of Arsenal?

His admission that he contemplated retiring from international football after Euro 2004 confirmed to those who alleged as much that his heart's not quite in it for France, that his priority these days is Arsenal, notably the fulfilment of their Champions League aspirations.

He has, after all, done it all in international terms. He's won the World Cup (although he wasn't picked for the 1998 final) and he's won the European Championship. For Zinedine Zidane, Marcel Desailly, Lilian Thuram and Bixente Lizarazu that was enough. They retired.

Maybe it was enough, too, for Henry? Ah yes, just what Ireland needs this evening: an aggrieved Thierry Henry, irritated by his doubters' questioning of his commitment to France, a Thierry Henry with something to prove.

If his response is emphatic, in the "Henry of Arsenal" sense, it could be a long, long 90 minutes for the Irish defence. And it won't have been the first time he made fools of his doubters.

In an interview with the Observer, Nick Hornby, the author and Arsenal fan, recalled Henry's early months at the club, after his transfer from Juventus.

"He was so hopeless. My brother said we'd spent £10 million on the French Perry Groves," said Hornby.

"His speed actually made things worse for him because it constantly got him into positions where his ineptitude was revealed for all to see."

Highbury, then, was beginning to question Arsene Wenger's judgment. Before signing Henry he'd confirmed that he was interested in buying Robbie Fowler or Emile Heskey. Nothing having come of those would-be deals, it was looking like he'd bought a poor consolation prize.

"Please end my boy's Arsenal hell," read the headline over an interview at the time with Henry's mother, Maryese.

"I worry about him - his head needs to be free of troubles for his feet to work on the pitch," she said, revealing that he was desperately missing his Monaco-based cats, Jungle and Reglisse, and his then girlfriend, Sabrina. In that order.

"Henry has struggled to make an impact at Highbury . . . he has been in and out of the Arsenal side this year after suffering a miserable time in front of goal," said the paper, echoing the consensus that Henry was a waste of Arsenal's money.

For the player those first six months at Arsenal were, painfully, resembling his time at Juventus, which he joined from Monaco in January 1999. A month after his arrival in Turin the man who signed him, Marcello Lippi, was replaced by Carlo Ancelotti.

After he'd made just 16 appearances, mainly as a winger (Filippo Inzaghi and Alessandro Del Piero were the first-choice front men), occasionally as a wing back, much to Henry's own bemusement, Ancelotti was sufficiently unimpressed to agree to a loan request from Brescia for the 21-year-old.

"I am expected to win the title and I cannot give Henry what he needs, which is nurturing," said Ancelotti.

Wenger, though, was only too happy to step in and offer Henry precisely the nurturing he needed, having signed him once before at Monaco, where he gave him his debut as a 17-year-old, often playing him alongside David Trezeguet.

After just six months, then, Henry left Italy for England, for £2 million more than Juventus had paid for him just six months before. Such was Wenger's belief in the player.

He was to be the replacement at Highbury for Nicolas Anelka, who'd moved to Real Madrid. Anelka, ironically, had been Henry's closest friend, along with Louis Saha, when, as teenagers, they were at Clairefontaine, the famed French football academy.

While Anelka struggled in Madrid, Henry was faring no better in London; according to his mother, he just wanted to go home. Then Wenger, who had been trying Henry out on the left wing, switched him to a central role up front, left him there and, well, he scored 18 goals in 22 games after Christmas.

Suddenly Highbury marvelled at Wenger's judgment - and at Henry's ability. The "French Perry Groves" was blossoming, as Wenger always knew he would, into one of the finest players in world football. Highbury reminded itself of how close Wenger had been to signing Heskey or Fowler instead of the Frenchman - the thrifty Arsenal board would only ever have allowed one to be bought - and, collectively, said, "Phew."

With 27 goals in 66 appearances for France, not to mention the number of goals he has created, and with World Cup and European Championship medals to his name, Henry can hardly be regarded as an international "underachiever".

But, unquestionably, Jacques Santini and his successor, Raymond Domenech, the current French coach, have failed to get out of Henry what Wenger has lucratively extracted over the past five years. It is, though, too soon to judge the Domenech-Henry axis.

The psychologists would probably put that down to Henry's special relationship with Wenger, the man he describes as his "spiritual father" (the comparison with Alex Ferguson's rapport with Eric Cantona is often made, although, in terms of temperament, the Arsenal men are probably a touch more serene).

Henry believes he owes Wenger everything: for giving him his start at Monaco; for taking him away from the concrete gloom of his home town Les Ulis, south of Paris, where he was born a year after his parents emigrated from Guadeloupe in the Caribbean; for rescuing him from Juventus; and for transforming him into one of the best players in the world. He has repaid the debt with interest.

He fell out with his father, Antoine, when, as his agent, he persuaded his son to sign a pre-transfer agreement with Real Madrid while he was still under contract to Monaco. FIFA fined Henry £40,000 and while there was a frost in the father-son relationship Henry turned to Wenger, his Monaco manager, for guidance. Wenger obliged, even persuading the club to pay his fine.

Now? "Arsenal is my paradise," he says, and Wenger remains his "spiritual father".

If he can strike up the same affinity with Domenech, France, and Henry the international, will come alive again. If it doesn't happen the French will continue to ask: "Where is the Thierry Henry of Arsenal?"

Ireland will hope he doesn't re-emerge in Paris tonight.

"Thierry is the best player to ever pull on an Arsenal shirt. If there is a better player in the world I would like to know who he is." - Arsenal vice-chairman David Dein

"I think he is a fantastic striker - the exception becomes the norm with him." - Arsene Wenger

"The only way to stop him is with an AK47." - Graeme Souness

"Henry is able to do everything: scoring goals, giving assistances, crossing, and creating space for other players. And he fights for every ball. I've never seen a player in France like him." - Michel Platini

"Kneel down before the King." - Italian newspaper headline after Henry helped Arsenal beat Inter Milan 5-1 (November 2003).

HenryonHenry...

"Big boats everywhere, big cars, beautiful women, the sun, the sea, the famous people. Life could seem easy in a place like this and, even as a kid, I thought, 'Monaco might not be the best place to learn football'."

"I eat football, I sleep football, I breathe football. I'll even sit and watch an English Conference game."

"When you put on the shirt of France or Arsenal, you change. It's like a new skin. You become superman."

"Arsenal is my paradise."

"I can't stay in the box and wait for the ball. I just can't. I would die. I can't, I can't. I have to move. Even if I have to drop back and get the ball off our goalkeeper I will do it because I need to touch the ball."

Date of birth: August 17th, 1977

Birthplace: Les Ulis, France

Clubs: Monaco (1993 to December 1998), Juventus (January 1999 to June 1999), Arsenal (1999 to date)

France: 66 caps, 27 goals

International honours: 1996 European Under-18 Championships, 1998 World Cup, 2000 European Championships.

Club honours: French league (Monaco, 1997), English Premiership (Arsenal, 2002 and 2004), FA Cup (2002 and 2003)

Awards: 2000 and 2003 French Footballer of the Year; 2003 and 2004 Professional Footballers' Association Players' Player of the Year and Football Writers' Player Of The Year