Male careers in the movies have always been longer than female ones, but until recently there was only one real route to on-screen immortality – to the certified, gold-standard agelessness of, say, Cary Grant. (In North By Northwest, Grant, then 55, not only appeared opposite a woman 20 years younger than him, Eva Marie Saint, his screen mother was played by someone only seven years his senior.) The key principle is suavity: the refusal to break a sweat; sophistication with the faintest hint of self‑mockery; the actor letting us know that he is old enough to know how silly this all is.

There are still disciples following that path up the mountain to the sunny uplands of longevity – perhaps we should think of this as Mount Rushmore being reconfigured to include a huge stone likeness of Grant himself, like the ones he scrambled over so urbanely in North By Northwest. Over there, do you see? There are George Clooney and Hugh Grant (both 54) in their hiking shorts, clambering for dear life as the career shadows fall, and a little further down is Colin Firth (also 54), trying to make sense of the map. Richard Gere (65) is sitting cross-legged on a boulder and seems to be meditating, though he may just be taking a nap. Suddenly they all freeze (though with Gere it is hard to tell). What’s that sound? Gunfire. But it seems to be coming from further up the mountain, where the old-timers are plainly not putting their feet up.

There is now apparently no age limit to an action career in Hollywood. The expendables are no longer unemployables, and actors in their 60s and even 70s are high-kicking in can-can routines of choreographed violence. After making a third Indiana Jones sequel in his mid-60s, Harrison Ford was over 70 when he joined the grizzled crew of The Expendables 3 (with Sylvester Stallone weighing in at 68 and Arnold Schwarzenegger at 67), in which the mercenary group does battle with its founder, now resolved to destroy them. In Indiana Jones and the Kingdom of the Crystal Skull, the camera keeps its distance from Ford’s stunt doubles – the charisma of an ageing action star has more to fear from obvious fakery in fights than from facial close-ups, since not much more is required of him than rugged scowls and glares of baleful defiance. Ford’s return as Han Solo in a forthcoming instalment of Star Wars after a third of a century is a melancholy prospect, like someone dressing up in late life to match a graduation photograph.

Tom Cruise, now 53 and strongly committed to stunt work, has just appeared in a fifth Mission Impossible film and signed up for another. By the time of its scheduled release, in 2017, he will be as old as Bruce Willis was in the first RED film, when he was Retired (though allegedly also Extremely Dangerous, to complete the acronym of the film’s title). For Cruise it seems that the real mission impossible would be calling it a day.

A loophole seems to have opened up, almost a wormhole in the fabric of Hollywood space-time. Through this portal an entire generation of veterans is currently trooping – and it is Liam Neeson, 63, who has made the most drastic and yet the smoothest journey across the genre universe, with Taken and its sequels. Steven Spielberg’s Schindler, agonising over whether he might have managed to save one more life, has been made over into a killing machine.

Neeson’s Taken character is a civilian whose unending mission is to rescue and secure his family, which gives him the moral stature to justify any amount of bloodshed. At the beginning of the story, Neeson’s character, Bryan Mills, was presented as an overprotective father, unable to move on from a broken marriage and spending altogether too much time worrying about the safety of his teenage daughter, Kim, seeking to control her movements. This could be a psychological drama of divorce, but then it strays into Bodyguard territory when Bryan agrees to help out some old friends, who have been hired to provide security for a moppet pop star’s gala concert but are a man short. In due course, there is a murder attempt, fitting the Kevin Costner/Whitney Houston template, and a moment of intimacy in its aftermath, but this too is a false trail, revealing the hero’s combat skills but not yet explaining them (he is an ex-CIA operative). Two genre feints in a running time of only 93 minutes – that’s not bad going. Only when Kim (Maggie Grace) goes to Paris and is abducted does the film move up decisively in terms of octane rating. Neeson plays it grim and straight. As Gladiator showed, audiences attuned to romantic self‑sacrifice (a traditionally female character arc) will accept a fair amount of violence, and it also works the other way around, with the stereotypically male element willing to identify ungrumblingly with a man who has lost the love of his life and never looks for a replacement.

What’s Neeson’s secret? His physique? Hardly – he has never been one of Hollywood’s Shirtless Ones, hasn’t even spent much screen time in a singlet. No doubt he has a fitness regimen beyond what most civilians would contemplate, but he seems to have no interest in projecting bolts of testosterone to the back of the auditorium. He moves like a big man who has learned to be light on his feet.

He has had the advantage of a late start, though it can hardly have seemed like an advantage at the time. There were plenty of male stars from Hollywood’s classic period who could not easily be imagined young, among them the ones who most seem to symbolise integrity: Humphrey Bogart and Spencer Tracy. A young actor can embody idealism easily enough (James Spader, say, in sex, lies and videotape, Stephen Soderbergh’s 1989 drama of fetishism and repression) but integrity is something that needs to have been tested over time, if not actually by time. For actors such as Bogart and Tracy (plus James Cagney and Edward G Robinson, though less reliably virtuous), their heyday was middle age. Wrinkles formed part of their appeal, rather than undermining it. Maturity was their present tense, and they had no visual history, lacking Facebook pages to plunder their own lives and archive the mistakes of adolescence.

The fact that more people are living long lives does not necessarily make ageing easier, and stardom has become a complicated business, with any amount of toxic undercurrent, ripples of projected narcissism and rancour. Stardom has changed because fandom has changed. Fandom in cinema increasingly follows the model of Kathy Bates’ Annie Wilkes in Stephen King’s Misery, revealing devotion as something essentially raging and vengeful. Obsessive love becomes malign stalking. Fame has always had its drawbacks, but now it seems all downside. To be a celebrity these days is to be beleaguered and outgunned, to feel at the mercy of every stranger’s Twitter feed. Perhaps that’s part of the appeal of action roles to the mature performer. In a world of stalkers, it is tempting for the world-weary to fire the first shot.

Celebrity has become an incurable condition, without remission. I can almost find it in my heart to sympathise with film stars who ban eye contact on set, or from their staff. Fame is a treadmill, and having your own gym does not seem to make the legwork any easier.

When Charlie Chaplin was the most famous person in the world, he could get rid of his moustache and go more or less anywhere he wanted. When the Beatles were the most famous people in the world, they had to dodge the crowds, naturally, but that did not stop them taking time off without worrying too much about it. Publicity was still a dog that could be brought to heel – but now thousands of the world’s most famous people have no possibility of escape from the spotlight they once ran towards so trustingly. Even seemingly contrived experiments in leading a normal life, such as Paul McCartney sending his children to state schools, would be impractical nowadays. The time when a world-famous film star could announce her retirement, as Greta Garbo did in 1941, and live out her life in New York without being bothered, even though anyone who wanted to could discover her whereabouts, are long gone. Only death can break the spell.

When Gore Vidal said of Truman Capote that his death was a good career move, it was mere waspish provocation, but the same assertion could be made without irony about Jean Harlow, James Dean, Marilyn Monroe. The flesh-and-blood person is surplus to requirements once an icon has been created, and often becomes an active embarrassment.

The prophetic document of the transformation of fame from safe haven into torture chamber was Robert Aldrich’s hideous 1962 film Whatever Happened to Baby Jane?, in which a former child actor, now an angry old woman, imprisons her disabled sister. There had been conscious ugliness in films before, but if this was meant to be a star vehicle for Bette Davis and Joan Crawford, then the vehicle it most resembled was a hearse driven off a bridge. Its greatest effect lay in the sadistic gloating over the ageing of the actors, whose faces and bodies were showing the effects of the passing of time, which female film stars are not allowed to do. Davis, in particular, seemed punished by being put in childish clothing and portrayed as being trapped in the past, when in fact her screen persona had always been non-standard and her choices often inventive – her fading actor Margo Channing in All About Eve, for instance, was by Hollywood standards a stingingly honest portrait of vanity made monstrous by despair.

Sylvester Stallone, Antonio Banderas, Jason Statham, Wesley Snipes and Dolph Lundgren in The Expendables 3 (2014). Photograph: Allstar/Millennium Films

It is easy to feel that the main event of celebrity culture is now the showing-up of the failing flesh, and all the acclaim of youth and freshness that goes before is only a pretext. When identification fails, when the idol fails to retire gracefully, things can turn nasty. Films are so centrally about youth and beauty that ageing on screen is a real taboo. We do not feel sympathetic when our idols reveal themselves as mortal – we feel betrayed. They have let down their side of the bargain, and unless they find a way to negotiate a new contract with a degree of energy and grace, fans become feral.

This used to be primarily the experience of women in films, but these days there is almost as full a range of options and delusions available to male movie stars as to their female counterparts. We have seen male stars go too far down the path of plastic surgery, and others who have relied too much on what they were born with. There is the temptation to have a lot of work done, as revealed by Mickey Rourke to gasps of audience horror in The Wrestler. And there is the temptation to put your faith in Mother Nature and let it all hang out, as exemplified by Gérard Depardieu to gasps of audience horror in Welcome to New York.

There are pages on the internet about “celebrities ageing disgustingly”. One of the prime exhibits in this rogues’ gallery of blasphemers against approved self-presentation is Macaulay Culkin. What has this disgusting brute done? He just stopped being 10 years old, as he was at the time of Home Alone – a bit of bad behaviour he shares with everyone else who was born in 1980. Culkin has not even forced himself on the world’s attention with any great energy, unless voice-overs for Robot Chicken on TV count. He looks a bit rough, it’s true. It is enough that he was once the defining image of youth and innocence, and now falls short of it. In the aftermath of celebrity, privacy is not an option.

The current incarnation of youth in films is not in the equivalent of a John Hughes comedy, but in Richard Linklater’s high-concept movie Boyhood, in which Ellar Coltrane is made to age convincingly from child to man by the drastic decision to film him over 12 years. Linklater’s film seems to have outwitted the enemy, containing and controlling the poignancy of the passage of time, but that is just how it looks now. There is no inoculation against mortality on film, except, strangely, tragic early death. If Coltrane is spared that, then one day soon he will be snapped unshaven and with bags under his eyes, and then he will be all over the media world, the shaming image appearing alongside the dewiest frame of him from Boyhood.

What is it about Liam Neeson that gives him durability when those around him are derided for the solecism of getting older? If it isn’t his physique, then perhaps it is worth considering his face. A broken nose can have a whole range of overlapping meanings. It suggests a bad boy rather than someone who abides by the rules, though there are many ways of suffering a facial impact, and relatively few of them corroborate such a character sketch. The decision not to have the nose straightened seems to offer more reliable testimony of a character indifferent to vanity. Even if this is a false impression, a broken nose takes away the potential stigma of prettiness from a male face. It is certainly a mark of experience of some sort, and an imperfection that can somehow enhance appeal.

There is no facial characteristic that communicates, however misleadingly, fearlessness and lack of vanity in women. In film terms, experience seems to add to a man, but subtract from a woman. Men can have been around the block a few times, but women are condemned to the repetition of freshness. It is as if a man can live off the interest of the time and effort invested in making movies, with a real prospect of earning the adjective “distinguished”, while a woman is always spending the capital of her looks, jeered at when she runs into debt or has to buy back her youth from a surgeon.

Harrison Ford in Indiana Jones and the Kingdom of the Crystal Skull (2008). Photograph: Paramount

Heavyweight dramatic actors often venture into comedy as a way of extending their durability in the marketplace. Meryl Streep has turned herself, with some effort and after a fair few duds, into a performer who can raise a laugh, while Robert De Niro has by now spent more time spoofing his persona than exploring it. Self-parody has existed in the movies at least since Marlene Dietrich’s performance in Destry Rides Again (a 1939 western in which she stars as a crime boss’s girlfriend who is won over by earnest, non-violent James Stewart while he tries to impose order on a lawless town), but it is a new development for it to be a whole career in itself. Of course, it is tempting for writers and directors to protect their films against laughter by pre‑empting it.

Liam Neeson may or may not have a sense of humour – certainly his appearance on Ricky Gervais and Stephen Merchant’s Life’s Too Short on television was as excruciating as anything since De Niro’s turn as the deluded would-be chatshow host in Martin Scorsese’s The King of Comedy, but that was the desired effect. Comic relief is certainly not part of the organising principle of Taken and its sequels, though the incongruity of Neeson as a skilled assassin was built into the structure of the first film – something impossible to carry over into subsequent instalments of what has become a successful franchise.

The level of brutality in Taken is modest by Quentin Tarantino’s standards, and is excused in plot terms by a number of factors: the hero being far from home, one against many, racing against time and so on. But not every actor can make an audience accept the hero leaving a villain plugged into the mains after he has no more information to give, or shooting a woman without warning to make sure her husband understands the gravity of his situation. “It’s only a flesh wound,” growls Neeson, as if he had done no more than spill red wine on his hostess’s dress.

Bruce Willis, an actor reliant on wisecracks, can make sure that a film such as RED seems like light entertainment with added gunplay and punch-throwing, but there is an awkward moment when Willis produces a bag full of severed fingers in order to identify the bodies of the men who have rashly just ambushed him. Liam Neeson’s Bryan Mills does not do anything quite as cold-blooded as mutilating corpses, but if he did, we would not be shielded from it by the directors of the Taken series – Pierre Morel, replaced in the sequels by the wonderfully named Olivier Megaton, both protégés of Luc Besson, Frenchmen shrewdly recycling American film tropes for the US market. Willis has been quipping his way out of moral ambiguity since the romantic comedy TV series Moonlighting three decades ago. Neeson is much less of a known quantity, certainly in action roles, and at their best the Taken films move him back and forth across the boundary between defensible and indefensible violence, never quite losing sympathy, nor ever quite taking it for granted.

What quality can turn an earnest middle-aged actor into an action hero? Gravitas is the indispensable element in this context: the moral stature that can complement physical power and even make it irrelevant, which seems to be viewed culturally as a male preserve. This quality is hard to define, though, even as it applies to men. Perhaps it is simplest to describe it in negative terms, as “what Tom Cruise will never have”. Some have gravitas and some do not. Boyishness and gravitas do not go together, and an eager-beaver manner kills it stone dead. The script of the 1992 film Far and Away, for instance, required Cruise, in desperate straits, to assert his authority over a horse by punching it (the setting is the Oklahoma land rush, and he is in a hurry to stake a claim). As a bit of business, it simply didn’t come off. There were film actors at the time who could have made it work, and they are the same ones who could get away with it today, nearly a quarter-century on: Clint Eastwood, Sean Connery, Harrison Ford. It is not a matter of physical strength – after all, no horse is actually being hit. It is down to gravitas: old-style stardom without benefit of moisturiser.

Gravitas is an accumulated heroic presence that can act as both armour and arsenal. How many people, for instance, watching Clint Eastwood in The Gauntlet in 1976, noticed that, while protecting a key witness in a mob trial, he never shoots anyone? Gravitas is a sort of abstract firepower that does not need to pull the trigger.

Tom Cruise in Mission: Impossible - Rogue Nation (2015). Photograph: Bo Bridges/AP

Is gravitas even possible for women in the movies? A woman in public life can embrace the physical signs of seniority as a badge of her seriousness, like Christine Lagarde of the IMF, who does not dye her hair and, as a result, appears to stand above the distractions of vanity. That, however, is not a possible strategy for an actor who wants to be cast in films. Even going ash blonde is a bit of a risk. Of the possible claimants, in terms of seniority and eminence (all of them older than Lagarde), Meryl Streep more or less disqualifies herself by her reliance on acting technique, her disinclination to establish a consistent persona across a range of roles. Helen Mirren relies on a disarming insolence, and her confidence that she will never run short of desirability seems justified so far. She can have a love interest her own age or, in RED, even fractionally older, and she is so offhand about it that nobody even notices how exceptional this is. Of this select group, only Judi Dench is defined not by being looked at but by looking. In her best work she outstares the viewer, astringent, judging, refusing even the admiration she has earned with her rejection of conventional approval. Female gravitas necessarily has a charge of wariness, and an actor who waited until after her 60th birthday for a leading role on the big screen (Mrs Brown, in which she plays the newly widowed Queen Victoria) will be warier than most. Dench escaped the workings of Stephen Sondheim’s law of female destiny in showbusiness, as spelled out in I’m Still Here from the musical Follies (“First you’re another sloe-eyed vamp / Then someone’s mother, then you’re camp”), and that doesn’t happen by taking anything for granted.

There seems to be a shortage of intelligent presentations of older women to a grown-up audience. Anyone who has seen Pedro Aldomóvar’s Women on the Edge of a Nervous Breakdown will have seen the director’s cheeky casting of Francisca Caballero – his mother – as a television newsreader. Women who work in front of a television camera and are unwise enough to pass their 40th birthdays are losing their jobs all the time, but one look at Almodóvar’s film should convince any sensible person that newsreaders in their 40s are not slightly too old, but much too young. What you want, when it is time to hear about the day’s events, is not some glamourpuss but someone who has been around for a bit, someone who has seen a few things in her time, a few wars, floods and Oscar nominations. It gives a bit of context, a sense of proportion.

Film-making, of course, is not about proportion. Stardom has strange acoustical properties that variously amplify, suppress and distort the frequencies of the personality involved. It is hard to turn such an apparatus into a loudspeaker for consciously conveying messages, though it has sometimes been tried. Subtext needs to stay buried. When Mark Rydell’s On Golden Pond brought Jane and Henry Fonda together on screen in 1981, the family reunion seemed to stand in for something more ambitious, the rehabilitation of a prodigal daughter. The star who had aligned herself most intensely with the counterculture of the 1960s, Hanoi Jane herself, was sending the message, using her father as a stand-in, that all she had ever wanted was to be loved and accepted by conservative America. No wonder the film felt strained – it had an agenda as fraught as the AGM of a failing company.

Film stars, offering themselves as screens on to which audiences can project their fantasies, cannot expect to control the process, except in the most indirect way. A shrewd film star is both a work of art and its curator. The supreme practitioner in this line must be Marlene Dietrich – when you hired her, you got her lighting man, too, so that she retained full control over the product. Alongside the erotic mystique, she had a strong hausfrau side, which did not show up on film, but she certainly kept her glamour swept and dusted. That professionalism extended to her home, where she received visitors in a chair placed under a spotlight, with a silver stripe painted down her nose to correct the proportions that did not meet her standards. Without any such crude mechanisms, Cary Grant maintained an astonishingly consistent persona over the decades, defending his narrow range (stylised ease, controlling suavity) against any possible challenge.

It can happen that stardom simply evaporates, leaving talent intact, which would be one way of describing Al Pacino’s career – he is still a performer with magnetism, but has shed what made him so fascinating in the 1970s, a physicality with elements of both the innocent and the wild. And sometimes a star persona takes a dogleg, moving into new territory without an actual break. John Wayne’s last starring role, in The Shootist (1976), for instance, was enriched by the cancer diagnosis shared by the actor and the character he played. Sometimes a film star can have two different and contrasting heydays, as happened with James Stewart. In his early career, up to The Philadelphia Story in 1940, he embodied an idealism that did not necessarily exclude slyness (in The Philadelphia Story, as the reporter at the society wedding, he makes divorced roué Cary Grant seem smug and obvious). When he started making films again after his distinguished military service, he had changed. He was like a bell with a hairline crack, the fundamental note unchanged, the overtones tending to jangle, and offering rich new resonances of uncertainty (Vertigo), strained folksiness (Anatomy of a Murder) and despair (It’s A Wonderful Life) to the directors he worked with.

The first Taken film was made before Neeson’s wife, Natasha Richardson, died suddenly in 2009. If it seems crass to connect a film star’s changing persona with his life experiences, then it is a crassness that was built into the workings of stardom even before modern communications made sure that there was no such thing as a secret sorrow. Film is porous. An event such as Neeson’s bereavement echoes backward in time, filling his segment of Love Actually (widowed father tries to teach his son how to approach the girl he is besotted with) with new associations, though it is anything but classic material in itself. His persona has been enriched with pain and the guilt of the survivor, which adds depth to the action hero’s trump card, the willingness to take punishment. He wins not because he is the better fighter, but because he doesn’t care about himself. Neeson’s presence was always sombre rather than blithe, so that the sorrow and strain we project on to it only accentuates what was there before. To have gravitas means to inhabit your history, and not to be diminished by your losses. And if that isn’t quite the same thing as real-world maturity, on the big screen it is the best we are going to get.

• Follow the Long Read on Twitter at @gdnlongread, or sign up to the long read weekly email here