It was after a neighbour shot her dog that Salma Hayek realised Donald Trump would become president.

“I thought it was a crazy thing, that it would never happen but then something really tragic happened to me,” she explains. “I have a ranch in America and a neighbour of mine killed my dog.” Hayek, who owns around 50 animals, including 20 chickens, five parrots, four alpacas, two fish, some cats and a hamster, says that Mozart, the tragic German Shepherd in question, had never attacked anyone. “And the authorities in dealing with the neighbour, and what he did… How is that legal? [Police have said the neighbour shot her dog after he found it fighting with his dogs in his garage.] Just to understand what was the normality of things. I realised in this moment, ‘Oh my God: he’s going to win.’”

I challenge anyone not to fall in love with her because (a) she’s a polymath and (b) she kicks ass

Hayek, a Mexican immigrant to America who identifies as half-Spanish and half- Lebanese, lives in London and is married to a Frenchman – who happens to be François-Henri Pinault, billionaire CEO of the company that owns Saint Laurent, Stella McCartney, Gucci – is perhaps uniquely placed to have firm views on Trump, Brexit and immigration, and we’ll get to them.

Hayek is primarily here this morning to talk about her new movie, The Hitman’s Bodyguard. We are at a press junket for the film. Elsewhere on the first floor of this smart London hotel are Samuel L Jackson, Ryan Reynolds and Gary Oldman, answering questions. Junkets can be dispiriting, and rapport can be in short supply. That is, unless you’re Salma Hayek, whose personality could light up a funeral. She arrives in a riot of black and red polka dots, tottering shoes and glossy hair, 5ft 2in and somehow 50 years old, although agelessly beautiful. She plonks herself into an armchair, hoists her legs up, and proceeds to tug the small table between us towards her. “Do you mind? They’re bringing me food. I like my food.”

Hasn’t she had breakfast?

“I did but I’m still hungry,” she grins.

A round of avocado on toast is spirited into the room, accompanied by a mystery shake in a plastic container. (A second round soon follows.) Famous since she was a soap star in Mexico in her 20s and with 40-plus Hollywood films to her name, Hayek has done literally thousands of interviews. What does she make of the publicity circuit?

“I’m good!” she says. “I just pretend I’m having a conversation with a new friend.”

Other half: Hayek and her billionaire husband François-Henri Pinault. Photograph: Tony Barson Archive/WireImage

Indeed, Hayek proves impossible not to like. She may be the perfect chat-show guest: various presenters have hooted along as she’s shown off pictures of her Donald Trump piñata, discussed her experience as a late-developing teen immersing herself in holy water and praying to Jesus for breasts, or confessing she accused Monsieur Pinault of having an affair after discovering text messages from “Elena”, only to discover Elena was a language-teaching app.

In fact, we have Pinault to thank for Hayek’s turn in The Hitman’s Bodyguard. The comedy-action caper is basically a mismatched buddy movie for Jackson and Reynolds, hitman and bodyguard respectively. Hayek is only in a few scenes, but as Jackson’s imprisoned criminal wife she matches him profanity for profanity.

“I think Salma steals the whole movie,” says director Patrick Hughes. “I challenge anyone not to fall in love with her because (a) she’s a polymath and (b) she kicks ass.”

“I have to tell you: action is not my favouritest [sic] genre of films,” Hayek says. “But I married a man who really likes them. So I became an expert. So I see them all!”

The image of fashion’s most powerful CEO spending his downtime like this is intriguing. What is his favourite action movie?

“Oh, it’s like Sophie’s choice for him, I think.”

What about Die Hard, I suggest.

“Oh, he loves Die Hard. But we love Bourne.” She claps her hands. “Sometimes he doesn’t even like [a film], he says: ‘Oh my God, that was so bad!’ But he still has to watch the whole thing.”

It’s a man thing, I say.

“Yes! My brother likes that one, my father likes that one… and because of that, when we were doing [The Hitman’s Bodyguard] I was able to say it was going to work, because it had a lot of the stuff that the good ones have.”

Mexican heroine: Hayek playing Frida Kahlo in Frida with Alfred Molina as Diego Rivera.

Similarly, do actors always know when they’re making a turkey?

“Oh yeah!” Hayek says, crunching through her toast. “Yeah, yeah, yeah, you know. And unfortunately I’ve never been wrong!”

Her CV is mixed. The first Mexican actress to break into Hollywood since Dolores del Río in the pre-sound 20s, she’s played a lesbian taco in the kids’ film Sausage Party and so-so roles in films such as Spy Kids 3D and Wild, Wild West. But she also earned an Oscar nomination for Frida, her 2002 portrait of Frida Kahlo, and The Hollywood Reporter has just tipped her for 2018’s awards season for Beatriz At Dinner, in which she plays an immigrant who clashes with a self-made billionaire.

At first, she says, she hated being famous. “This was terrifying because in Mexico when you do a soap,” – at this point she leaps out of her chair and heads for the door – “Don’t worry, I’m not escaping… Hello?” Her security guard appears with a pack of American Spirit cigarettes. “My soap was seen by 60% of the country, so it’s every day, in their house. Do you mind? Do you want one?” she says, offering the smokes. “So you become very familiar, like you’re their cousin or something. I’ve never been so famous since. I kind of hated it.”

Taking aim: Hayek in The Hitman’s Bodyguard. Photograph: Rex/Shutterstock

If she hated the attention so much, I wonder why she headed for Hollywood. But Hayek is battling with the curtains while she attempts to heave open a sash window so that she can smoke, unlit fag in her mouth. Not relishing the idea of Hayek tumbling on to the streets below, it seems only polite to help. For a few seconds she holds back the curtains, while I struggle to wrench the window.

“Oh my God, that was so easy,” she says. “I really did want to be an actress, not just ‘be famous’. It’s a different thing. Because I was famous on a soap! That doesn’t make you a great actress. So I went to America to start all over again.”

This was the 90s. She played extras and enrolled in the Stella Adler Academy Of Acting in LA, alma mater to Marlon Brando and Robert De Niro. “And this is how old I am, she [Adler] was still alive! She was 90 and she was still teaching and flirting with the young boys. She was a tough cookie but she was brilliant.”

Hayek could barely speak the language - “My English sucked” – worse, there weren’t any parts. Mexican women played maids or gangster’s wives. “And that’s if you got lucky.”

Hayek threatened legal action against one director.

“I was screen-testing for the lead in a film and they said that it was not written Latin, but they wouldn’t mind changing it. I learned the script but when they sent me the pages [for the audition] there was none of the things I had learned, it was another role. So my agent called them and they said, ‘Are you crazy? She’s Mexican. We can change [the race of] the bimbo, but not the lead.’”

Fashionista: at Stella McCartney, spring/summer 2016, Paris fashion week. Photograph: Bertrand Rindoff Petroff/Getty Images

She got her agent to call back. Would they please just give her five minutes to audition for the part she’d learned?

“And they said, ‘Absolutely under no circumstances.’ So I said, ‘OK, you tell them that they either see me, or I’m going to sue them.’ And they said, ‘There’s no point in her coming, even if she had been the best audition she would have never gotten the part… but now we hate her. Does she want to come knowing that we detest her?’” They kept her waiting for five hours. They wondered why would she do this to herself.

“I’ve never said this to anyone, the name of the director, but it was Ivan Reitman. And I said, ‘Well, I thought that the director that could see Arnold Schwarzenegger and Danny DeVito as twins [1988’s Twins], and Arnold Schwarzenegger giving birth to a child [1994’s Junior] maybe could see a Mexican as a fashion editor.’ I thought I owed it to the new generation of Mexicans. That if I got this right, maybe something will shift.”

Years later, she bumped into Reitman and he apologised. “We had such a lovely conversation, he was so elegant,” Hayek says. “He said, ‘I was wrong.’”

All of this pales next to the hill she climbed for Frida.

“I was obsessed,” Hayek says. “I was endeavouring to do a film about an artist in a time when all the films about artists had failed. Already [the studios] were going, ‘Oh no.’ Then I’d say, ‘It’s a period piece – about Mexicans! And they’re communists! It’s a love story between an overweight man and a woman that limps and has a moustache!’”

Committed: Hayek campaigning for women’s empowerment with Gucci’s Frida Giannini and Beyoncé. Photograph: Ian Gavan/Getty

One studio did eventually take it on, Edward Norton (her partner at the time) rewrote the script for free and Hayek called in favours from co-stars including Ashley Judd, then one of Hollywood’s most bankable faces. It opened in two cinemas. Its success, I suggest, must have been all the sweeter.

“Yes,” she says. “Because [the studio] dismissed it. I didn’t even have a poster!”

It may not surprise you to learn that Hayek is a committed activist: her list of charitable endeavours is too long to go into here, but it includes her own foundation helping women and children in Mexico, and the feminist charity Chime For Change, founded with Beyoncé. “It’s so massive I don’t even know what to tell you. I don’t just do awareness, I actually do strategy. I’m on the board. It takes a lot, a lot, a lot of time.”

Other projects receiving the full force of the Hayek commitment include her range of nutritional juices, and a beauty line which she created herself. She also has her own production company, which helped turn the TV show Ugly Betty – based on a Colombian telenovela – into a worldwide hit. I ask where this drive comes from.

“It’s been there since I’ve been a child. A sense of justice and responsibility for the human race. How can we be better? Because a lot of people don’t think that way. They think: ‘How can I pay less tax?’ And so when I see things that make me think we are degrading and degenerating mentally it makes me want to do something.”

She has been hugely successful. She’s married to one of the world’s richest men. (Their daughter, Valentina, attends school in London.) She could just put her feet up. Of course, it’s a cheap question – we already know the answer.

“Why would anybody want to sit around and do nothing?”

Hayek says that she made it clear she would always remain financially independent from her husband, whose net worth is around $17.3bn. Which may explain money-job films like Sausage Party.

Mirror mirror: Hayek guest stars in Ugly Betty with America Ferrera. Photograph: Danny Feld/ABC

“At the time I met him, I had already decided I didn’t want one of those [ie a husband],” she says. “I had set myself up for a completely different life. I was ready to live on my ranch that is a sanctuary for abused animals. I would come to LA and work a little bit. I was not planning on spending. I had no interest in jewellery or clothes or cars. I had everything I wanted. Maybe I had a guy here or there. I also thought I couldn’t have children. Then he [Pinault] came along, swept me off my feet, changed my entire universe and knocked me up.”

Can she remember what they first liked about one another?

“Yes. I asked him, if he had not been doing what he was doing, what would have been his dream? And he said an astronaut – and that was my dream! Then we started talking about different theories of physics, which is my secret passion. And soccer! I’m a huge soccer fan [she supports Arsenal]. Just random things that nobody knows I like. It was just magical.”

As a global citizen at a time when the world seems to be closing in on itself, is Hayek optimistic for the future?

“Very optimistic. I have to look for the positive about everything.”

Hayek campaigned for Clinton. How’s it going to end for Trump?

“I can promise you he’s not going to build the wall. You cannot build it without the Mexicans that are illegally in the country. That is what makes the economy so strong because they are paid less than half, with no benefit. It’s just not going to happen!”

Hayek is banging her fist on the table.

“His days are numbered! Even if he becomes a dictator and rewrites the constitution and now the presidents can stay 12 years! Still his days are numbered!”

Salma Hayek: activist, actor, producer, juicer, businesswoman, friend to the animals and all-round proper laugh. You wouldn’t mess.

The Hitman’s Bodyguard is in cinemas on 17 August