Michael Caine is 88 and walks with a stick. He has a gammy leg and a dodgy spine and reckons the only time he leaves the house these days is when his wife has the time to take him out for a drive. The other week he was sent a screenplay that had his character running away from a bunch of crooks, and this made him laugh – the very idea he could play it. “I can’t walk, let alone run,” he says. “And I’m more or less done with movies now.”

He was winding down anyway, hadn’t shot a film in a year, and then sneaked in one last movie, Best Sellers, just before the pandemic struck. He doubts he will ever make another, which is fine by him, no great loss. He’s got his knighthood and his Oscars; what does he have left to prove? He says: “I’ve done 150 movies. I think I’ve done enough.”

Caine has been such a reliable fixture for so long – part of the furniture, a familiar face on the screen – that it’s unnerving to imagine the landscape without him, like walking into the Tower of London and finding the ravens all gone. It’s more unnerving still to realise that it may already have happened; that he might have retired without anyone making a fuss. Caine spent the first part of his career storming the barricades and the second enjoying the spoils of his success. One would have expected some big final act, a showstopping swan song. Instead, we have this: a clean getaway.

The actor is speaking via video link from his Surrey home near Box Hill (the first time, he says, he has done an interview this way). He’s supposed to be promoting his role in Best Sellers, an amiable enough enterprise that casts him as a dyspeptic old author who becomes a viral sensation. But the man’s not feeling it; he seems to have moved on. When I tell him I’ve heard he based the character of Harris Shaw on a monstrous old director he once worked with, he pleads total ignorance and says he can’t think who I mean. “I don’t remember. I might have done. It’s been two years since I did it, so it’s funny talking about it now.” He slurps his tea. “Also, I’m 88. My mind’s not as agile as it used to be.”

You see, he adds, that’s another thing to consider. “I mean, I’m fine, I’m well. But I can’t walk and I can’t stand for very long and now I don’t know whether my bloody memory’s going. And I’ve worked with people like that. I worked with one actor who had all his bloody lines written on the wall because he never remembered any of them. And there are others who wear earphones and have the assistant director read the next line to them. Johnny Depp – he does that [Depp, for his part, has suggested otherwise]. I can’t remember who the other bloke was. Older American actor. It was a long time ago now.”

When lockdown happened, Caine was faced with a choice. He could either lounge about in the house and watch telly all day or he could add a fresh string to his bow. So he sat and wrote a novel, a thriller, his first stab at straight fiction after a number of memoirs. Fingers crossed, he’s getting it published next year, although he’s still rewriting and tidying, making it look more professional, “Paragraphs,” he says, chuckling. “Punctuation, all that.”

What’s the title and what’s it about? “Well,” he says. “The title is If You Don’t Want to Die. I only read thrillers. I’m an adventure man, I’m not a literature person, so I’m not trying to replace Shakespeare here. But it’s based on something I once read about two dustmen, two rubbish collectors in the East End.” Dramatic pause. “And they find uranium in the rubbish.”

As a boy in south London, his twin passions were always movies and books, the cinema and the library. He’s done cinema to death, so it’s only fitting that he should now be circling back to the library, albeit metaphorically – the actual building has long gone. The last time he visited Elephant and Castle he saw it had been replaced by a block of flats. But that’s progress, that’s history. It involves good changes and bad. When he was starting out as an actor, for instance, British film and theatre were the preserve of the posh. “It was: ‘Bunty’s having a party and everyone’s in their tennis whites.’” Another short laugh. “Then we came along and we changed all that.”

These days we view Caine’s early career in sweeping historical terms. He was the ordinary bloke with the alleycat swagger, the working-class hero with the undiluted Thames accent, a bespectacled poster-boy for 60s social mobility. He has now reached the point where he’s started to view himself in those terms, as part of an upstart generation of actors that included Albert Finney, Richard Harris, Peter O’Toole and Tom Courtenay. Whereas at the time, of course, he was living his life in closeup; no perspective whatsoever. “I was just in the disco, pissed,” he says. “I didn’t know what the hell was going on.”

Sometimes, channel surfing, he’ll catch a glimpse of an antique Caine classic. It might be him playing deadpan Harry Palmer in The Ipcress File, hardcase Jack in Get Carter, or rollicking, ill-starred Peachy Carnehan in The Man Who Would Be King. But he says he has no interest in revisiting old glories and can rarely be persuaded to look back at his work. He reckons that Alfie was probably the best film he made, but he’s basing that on memory and hasn’t updated the files. “I’ve only watched Alfie maybe two or three times.”

What he misses, if anything, are the people, not the films. The films are there on his iPad any time he wants to watch them. But his mates have absconded; they’ve made their getaways, too. “My generation is going. All my friends are dying off. Because we all got so old. Roger Moore, Sean Connery – those are two of my closest friends who went. Then a couple of days ago, Johnny Gold, who owned Tramp, the discotheque in London. And I have another very close friend who is very, very ill. If he survives until next weekend I’ll be surprised. And I won’t mention his name, but you’ll read about him in the papers.”

I ask if he thinks the country is in a better shape today than when he started out, or whether the social progress he epitomised has since been rolled back. “I don’t know,” he says. “It’s still not perfect. Probably never will be. Look at the state we’re in now. If you’re growing up today you’re in for a tough time.”

In the past, Caine has variously described himself as a leftwing Tory and a rightwing socialist. He traditionally (but not exclusively) votes Conservative. He adored Margaret Thatcher, respected David Cameron and voted leave in the 2016 referendum. One day, I suggest, he’s going to reconsider that position, but he’s having none of it. He still fully supports Brexit, despite the current supply-chain chaos, despite the burgeoning winter-fuel crisis.

“Oh, that’s teething trouble,” he assures me. “It’s obviously not going to go well immediately.” Then he slightly shifts position. “I mean, I don’t know what’s going to happen. I’ve got to wait for Boris to come back off holiday. I mean, to do that, to go on holiday right now, it’s unbelievable. Empty shelves. People queueing for petrol. And you think: ‘Wait a minute. He’s gone to Marbella?’”

So wait – he thinks Brexit is good, but he’s unimpressed with Johnson personally? “Oh, I supported him. I thought he was great. But now I’m very disappointed in him. He made a big mistake there, going to Marbella. Let’s see if when he comes back he can settle it all. Otherwise we might have a socialist government.”

And he might be voting for it? “Might be. You never know. I did it before. I did it with Blair. I did it with someone else. I forget who – it was a long time ago. I always vote according to what I think. What’s good for us. What’s good for the country.”

He is, I suspect, your classic working-class Tory – raised in poverty, a self-made man. This perhaps partly explains the mass of substandard pictures that clog up his CV – quick-cash gigs such as The Swarm and The Hand and Jaws: The Revenge, which he was off shooting the night he won an Oscar for Hannah and Her Sisters in 1987. If you’ve been brought up poor, money must matter more. You want to amass it. You want to keep it. Maybe he feels that there’s somehow still a lack.

“No, no, no,” Caine objects. He doesn’t think that at all. He’s flush with cash, awash with cash. “I’ve always lived to the highest limit that my money would allow. I mean, I’m not extravagant. I’m not silly. I’m not out buying caviar every day. But yeah, I’m talking to you from a great big house with 24 acres of land. Which is fantastic because it means that my grandchildren can come and visit, and they disappear instantly and just go running around. Two miles, running round and round the garden.”

Once again, he checks himself. Here he is waxing lyrical about his house in the country, when the reality is that the place has now run its course. He bought it 30-odd years ago as a big family home, large enough to accommodate him, his second wife, Shakira, his two daughters and three grandchildren. These days it’s mostly just him and Shakira, rattling around. “So I’m going to get a smaller one,” he says. “Because the grandchildren have all gone now. They’re all growing up. So I’m going to move back to be nearer to them, where it’s easier for them to visit. I’m going to move to Wimbledon. My daughter, Natasha, lives in Wimbledon.”

He was named Maurice Micklewhite, after his father, who worked as a fish market porter. I’ve read that he only officially changed it a few years ago, because he got sick of having to explain himself every time he lined up at UK passport control. But he says that’s not true: he changed it ages ago, 10 years back at least. It felt like cutting the last link with his past.

When he first became Michael Caine, of course, people still called him Maurice. “But I haven’t got any family members now, so no one’s called me Maurice for years. Everyone’s dead. My brother, my mother, my father. If I have any other relations, they’d be living in Bermondsey.” He shrugs. “And I don’t go to Bermondsey.”

What about him? Is he still Maurice deep down? “No. The day I became Michael Caine, that was it – I was Michael Caine. I wasn’t Maurice any more, I was a completely different person. And it was amazing. It was fabulous.”

What was wrong with Maurice? “Well, nobody knew him. He was broke. He was out of work. And the moment I became Michael Caine, I got a job and was on my way.”

He swings with practised ease into an anecdote he has probably told 100 times before – at dinner parties, in discotheques and on prime-time chatshows to rolling audience applause. It’s the tale of how he got his big break in the 1964 film Zulu. How he met the American director Cy Endfield in the theatre bar only to be told that the part he wanted had already gone to another actor. How he had thought that was that. Back to penury and obscurity. Back to being Maurice Micklewhite.

He says: “My entire movie career is based on the length of the bar at the Prince of Wales theatre, because I was on my way out and it was a very long walk to the door. And I had just got there, when he called out: ‘Come back!’ because he had decided that I could play the part of the officer instead. He said: ‘You look like an officer,’ because I was 6ft 2in, blond hair, very slim. The door was half-open; I was very nearly through it. I turned around and walked back in.”

His story makes me think of Dick Whittington, turning again on the road into London. “Exactly,” says Caine. “That’s exactly who I am: the Dick Whittington of acting.”

• Best Sellers is available digitally on 18 October and screens on 27 October at the Raindance film festival.