Paradox player who is modestly vain

David Beckham's move to France is the latest of his self-promoting gestures. Or is it the engaging act of a thoroughly nice guy?

David Beckham has only played once at Old Trafford in an opponent's shirt since he left Manchester United, where he began the extraordinary career that has turned him into the most marketable footballer in the world. He was received with exceptional warmth by the fans of his old club when he came on to play for AC Milan. At the end of the match, Beckham reciprocated with one of the big gestures which have characterised his long and shrewd career.

He bent down to pick up a United scarf thrown to him on the pitch. It was not the usual red and white. It was green and gold – the colours of the fans' protest movement against United's American owners, the Glazers, who have saddled the club with £600m of Glazer family debts. Beckham innocently draped the scarf around his neck, to a delighted uproar from the fans. When the press later asked him about it he shrugged and replied, with faux-naiveté (he'd better brush up his French) that protests were not his business.

David Beckham has long been the master of the grand gesture, as we saw when he signed for the latest of his illustrious international clubs. After Manchester, Madrid, Los Angeles and Milan – the list makes him sound like an upmarket shopping chain, which is what, in a way, he is – he pitched up last week in Paris to join another mega-club. And the first thing he did was announce that he would be giving away his £4m PSG salary to a French children's charity.

It was a move of extraordinary deftness. Just as the actor Gérard Depardieu is quitting France because of its new 75 per cent tax rate another international celebrity arrives in Paris and makes a far nobler move. Little was said about the fact that his massive commercial spin-off earnings will only be taxed at 30 per cent. At LA Galaxy only $6m of Beckham's $46m annual income came in salary; the rest was from sponsorship, sales, image rights and other deals.

Beckham is no fool. He knows that the Qatari oil billionaires who own PSG are buying him as part of a strategy to turn the tiny emirate into a sporting and entertainment giant. "I don't see this as a short-term project," he said of his publicly announced five month contract. "I consider myself part of this project… helping the club become one of the biggest powerhouses in football." And he won't be doing that for charity.

Yet only the curmudgeonly would begrudge this. That is part of Beckham's immense charm and skill. It is only one of a succession of paradoxes about the world's most famous footballer. They enable some to characterise him as a washed-up, self-aggrandising, self-indulgent, over-groomed footballing chav with ghastly inked-arms – and others to see him as a role model father, ambassador royal and national hero with his shy smile and modest good manners.

Not everything that is said about Beckham is true but there are apparent contradictions. As a footballer, he brought disgrace with a petulant kick which saw him sent off and England crash out of the 1998 World Cup, and yet he was transformed from villain to hero when with the last kick of the game he scored the goal that allowed England to qualify for the World Cup next time.

As a fashion icon, he manages to be both naff and stylish. The man who sat with his Posh Spice wife, Victoria, on a golden throne at his wedding in an Irish castle, and whose home was dubbed Beckingham Palace, is a figure who looks good in anything, from a sharp suit to his oiled skin. He is "one of the world's most handsome men," said the editor of Elle, "loved by men and women alike".

Beckham's image is both straight and gay. The word "metrosexual" might have been coined for Beckham, who also happily posed for the gay magazine Attitude. In the tough macho world of British football he was the man who unashamedly wore sarongs, pink nail polish and panties belonging to his wife. "He was a fantastic lad till he got married," Man Utd's manager Fergie once muttered.

Beckham is a shy show-off. He has the bashful smile and downward eye glances of Diana. And yet this modest narcissist loves being looked at. That can be seen from his formative years. Introverted ex-team mate Paul Scholes, in his autobiography, accused Beckham of hogging the limelight after every goal. Even carrying the Olympic torch in a speedboat race up the Thames he looked like a dapper James Bond with an ironic smile on his lips – a sexy little smirk, one woman called it.

Yet his moisturised male vanity is offset by the vigour of his tattoos, more than 20 in total, including a gruesome fascistic eagle on his neck. Beckham speaks of this body boorishness with tenderness as he explains that most of them are tributes to his family: "When you see the tattoos you see an expression of how I feel about Victoria and the boys. They're part of me." It's another Beckham ambiguity. He wears his deep love for his family as if it were a fashion accessory.

Another contradiction: he is self-focused and selfless. Beckham suffers from obsessive compulsive disorder to such a degree that all the cans of Coke in his fridge have to be turned with their labels facing the same way. But he has an extraordinary selflessness too. When a torn Achilles tendon took him out of the 2010 World Cup he did not sulk but accompanied England as team mediator. When, after working so hard to secure the 2012 Olympics, he was omitted from the British squad he carried on cheerfully in supporting roles. He visits troops in war zones and works for Aids and malaria charities.

For years, a running media gag is that Beckham, the son of a kitchen-fitter, is a bit of a fool. Watch his most recent interviews on French television, and you will see the lie in that. Behind the Chingford accent and the plain words is a keen intelligence, an intuitive diplomacy as well as a natural grace. David Beckham is a man for the paradoxes of our time.