As well as marking his return to the role of swashbuckling superhero that he made his own in The Mask of Zorro, the sequel reunites Banderas with director Martin Campbell and, most importantly, given their onscreen chemistry, with Catherine Zeta-Jones. But more of Ms Jones and Zorro later. First, what of that other Hollywood femme fatale in Banderas's life, his wife, Melanie Griffith?
Another surprise awaits me, for he is so open and honest and, well, genuinely sweet, when talking about Griffith, Tippi Hedren's troubled daughter who famously married Don Johnson aged 18, divorced him, married another actor, Steven Bauer, had a child, Alexander, now 21, then remarried Johnson and had a daughter, Dakota, now 16.
She and Banderas met while Banderas was married to the Spanish actress Ana Leza, Griffith was still married to Johnson. "Melanie is my soulmate and I am absolutely comfortable being with her, and I find her very beautiful. We have been now 11 years together - besides Paul Newman and Joanne Woodward, I think we are the oldest couple in Hollywood!"
Do you tell your wife constantly that you love her, that she is beautiful, to compensate for the industry you are both working in? "I do it, but I don't do it to compensate. I do it because I really feel it." He agrees that Hollywood is very cruel towards women, pointing out that Zeta-Jones's first role after Zorro was to play Sean Connery's love interest. "If you want to do it in the opposite direction," he says, "forget it."
So how did he feel when his wife set up a website chronicling with alarming honesty her various addictions, and her struggle to get clean? "I pushed her to do that, to be open," he says. "I say to her, 'You have this problem you have to share with people,' so she opened a page on the internet so people can talk to her, and I love her even more for that, for being courageous and for not hiding anything."
Banderas also gave Melanie Griffith, who is now 50, the confidence to end her other dangerous addiction: to plastic surgery. "Hollywood stars are not supposed to be perfection, I don't believe in perfection, I think it is a mistake. So, since we are together, she hasn't had any plastic surgery. I said to her, 'I want to see you growing old and I will grow old with you too, and I don't care.' I like her the way she is, wrinkles are beautiful."
They have a daughter together, Stella, who is now nine, and he says he missed her desperately when he was on the fivemonth Legend of Zorro shoot in Mexico. The £60 million film, set in the California of 1850, is that rare thing: a sequel that is better than the original, with a charm reminiscent of old Douglas Fairbanks movies and a great villain in the shape of British actor Rufus Sewell. It's out at the end of the month, in time for half-term, and is sure to be a big family hit.
Banderas did many of the stunts himself, especially when his double broke his leg during the shooting of the climactic set-piece on a runaway train. But he bore his bruises well, and that may have something to do with working with Zeta-Jones again. The first Zorro movie, in which she played Banderas's onscreen wife, Elena, launched her as a bona fide Hollywood star, and made $250 million at the box office. When Banderas and I meet, Zeta-Jones is just along the hall at the Dorchester.
"The quality I like most is not her beauty, which I recognise totally, but that she is very witty, very funny, and that she didn't change, not one leetle bit, when she became famous."
It turns out it was Banderas who introduced Zeta-Jones to her future husband, Michael Douglas. "We were at a film festival in France, presenting the first Zorro, and Michael was there. He took me outside and said, 'Who is that beautiful girl by your side? Can you introduce me?' He owes me, big time."
Why, though, did they wait seven years before making the Zorro sequel? "The script had to be right, it had to be funny, tongue-in-cheek. When I learned that Zorro and Elena get divorced in the first few minutes, I think, yes!" he says, rubbing his hands together. "Now we can have some fun."
Zorro is a long way from the sort of lowbudget, independent films Banderas made in his native Spain, including five with his mentor, the director Pedro Almodóvar.
But when I ask him if he feels he has been typecast since arriving in Hollywood, speaking not a word of English, in 1992, he shakes his head and lights another cigarette. "Yes I have played Zorro and Pancho Villa and Che and El Mariachi.
The Latin hero is OK, I don't mind that, but when I arrived in America many other Latin actors said my fate is to play the bad guy, but I didn't allow them to discriminate against me. I have also played a homosexual [in Philadelphia], done children's films [Spy Kids and Shrek], appeared on Broadway. So, no, I don't think I have been typecast. Latin actors have a place in Hollywood now, you have Salma Hayek, Jennifer Lopez, my old friend Penelope Cruz."
Does he not think, though, that he has made some dubious choices since arriving in Hollywood? Most notably, his role in Emma Thompson's Imagining Argentina, described as a "cult classic of awfulness"? Or the risible The Body, for which he was paid $12 million, which meant there was no money left over for anything else? He merely shrugs.
Banderas was born in Malaga, the son of a secret policeman and a teacher, and grew up under the Franco regime. "When General Franco died I was 15 years old, it was only when I was older I realised how trapped we were. We only had one TV channel, and very little information from the outside world - we didn't know the horrors of the regime, at the time it seemed normal."
At first, he wanted to be a professional footballer, but an injury meant he turned to his second love: theatre. He attended the local school of dramatic art and later moved to Madrid, where he joined the prestigious National Theatre of Spain. He was spotted and cast in his first film,
Labyrinth of Passion, by Almodóvar. He feels fiercely proud of his Spanish heritage. "I still have a home in Spain, I spend a lot of time there. And although I haven't made a Spanish film for 15, 16 years, I am planning to
direct a film there based on the novel El Camino de los Ingleses, about a group of kids growing up in the Seventies."
I ask if he has taken any flak, in the wake of the Madrid bombings, from Spaniards angry that he is living in America under Bush. "I never had a journalist from Spain spitting in my face because I am working in America," he says.
"I am not supportive of the American administration, which is not an easy thing to do being a foreigner. I never left my country behind, I do not even have a green card. Some people thought that when I got married that was what I was looking for, but I didn't even apply for American citizenship."
Ah, back to Melanie Griffith. He says he is "trying to be a good stepdad" to Griffith's two children. Alex is in New York, studying to be a director, and Dakota is "at that terrible age where the hormones are raging, and she doesn't know whether to play with dolls or hit on the neighbour".
How can she not have issues about how she looks, growing up in a $4 million Tuscan-style villa in the Hancock Park area of Los Angeles, with a basket case for a mother? "I tell her how beautiful she is. Every day. And how much I love her and that I will always be there for her." And I am not sure now if he is talking about his stepdaughter or his wife. But I am inclined to think the latter.
• The Legend of Zorro opens on 28 October.