If there was a hero for our times, just what would he be like? Once upon a TV schedule, the time-honoured template of a smooth, charming and debonair ladies' man would have ticked every box. But in an era when even James Bond has been revealed as brooding and flawed, strong-jawed perfection is no longer in vogue.
As for a heroine, the sexy, sassy, wisecracking stereotype is so familiar as to be the stuff of cliché.
Today, audiences crave more complex characters, who think differently, act differently and who are fundamentally different from the rest of us in outlook and behaviour. Maybe that's why the "hidden disabilities" of Asperger's syndrome and bipolar disorder have become a defining attribute of the key protagonists in some of our most popular primetime series: Sherlock, Homeland and Danish-Swedish thriller The Bridge.
"On the one hand, this broader diversification of detectives is in line with the way society is evolving," says Esther Sonnet, head of the School of Creative Arts, Film and Media at the University of Portsmouth. "On the other, detectives have always been outsiders, who see life from a different perspective.
"[In addition] people with Asperger's have many of the qualities modern detective work relies upon: tremendous focus, an ability to concentrate on one thing to the exclusion of everything else and a dogged determination to get to the bottom of something that interests them," says Sonnet.
This might go some way to explaining why, when we watch The Bridge on BBC Four, it is actress Sofia Helin's faultless portrayal of Swedish detective Saga Noren that makes it so compelling. Blonde, beautiful with an intriguingly scarred face, Saga is methodical, driven, obsessed with detail and obviously brilliant at her job. Yet it's clear from her inability to read emotions or pick up on social cues that she's very definitely on the autistic spectrum.
What is interesting about the performance is that Saga's detachment doesn't make her unlikeable, just unknowable. Yes, she lacks empathy. But when her extraordinary genius fires off in every direction, it's impossible not to feel admiration for her intellect and, maybe, even a brief stab of envy at the freedom from office politics her condition confers.
"Anything that helps to increase awareness about autism is to be welcomed," says Jolanta Lasota, chief executive of the charity Ambitious about Autism. "But it has to be balanced by portraying people on different parts of the spectrum; as the saying goes, 'If you've met one person with autism, you've – met one person with autism.' No two people are alike."
Yet what The Bridge, Sherlock and Homeland do have in common is that they feature outsiders who don't conform to the narrow norms of what is usually presented in television drama. Indeed, when Sherlock, Benedict Cumberbatch's self-confessed "high-functioning sociopath", engages in flights of convoluted logic, leaving Dr Watson trailing in his intellectual wake, it's hard not to feel sorry for Martin Freeman's bog-standard "normal" character.
Charlotte Moore, mother of two adult sons, Sam and George, who are severely autistic says: "I know a 19-year-old girl who is very bright and has Asperger's syndrome, who is absolutely taken with Sherlock because she identifies so closely with him. There is a potential problem in portraying any 'type' of person with a condition as people inevitably think that they are all the same, but autism is a very individual thing."
'After Rain Man came out, people would constantly ask me, 'So, what amazing gift do your sons have?' All I could say was, "Do not sleeping or running away count?"
The 1988 film, starring Dustin Hoffman as the institutionalised Raymond Babbitt and Tom Cruise as his estranged brother, Charlie, marked a watershed in the spotlight it shed on autism. Or at least one sort of autism: the savant.
Some argued that it promoted a greater awareness of the needs and abilities of autistic people, others said it offered a simplistic stereotype. Similarly, their portrayal today can raise concerns. "Sherlock has made being different seem 'cool', which is great, but again there's a risk that people will now assume anyone on the spectrum is bound to have crime-solving skills," says Moore, who has written a book, George & Sam, about her life with the boys.
Nor is this a trend confined to the small screen. The 2005 novel Extremely Loud and Incredibly Close by Jonathan Safran Foer, which was made into a film starring Tom Hanks, is narrated by nine-year-old Oskar, who is prone to obsessions and finds making friends his own age difficult. Although undiagnosed as autistic, the implication is that he is on the spectrum and Oskar is aware that his brain is wired differently.
It is this inner conflict that helps lend greater light and shade to characters. Certainly in Homeland, CIA officer Carrie Mathison's behaviour – sometimes restrained and constructive, sometimes impulsive and destructive – is dictated to a huge degree by her bipolar disorder.
Carrie makes for a frustrating anti-heroine, but there's a truthfulness and a believability about everything she does, which keeps us (if only just) on her side, even when she knowingly exploits her sexuality. By contrast, in The Bridge, when Saga talks about sex, it is clearly in terms of her bodily needs rather than any expression of affection. Yet we see her poring over textbooks in an attempt to improve her interpersonal skills.
No wonder we're intrigued. These are no cookie-cutter characters. "Audiences are very sophisticated and they want protagonists who interest and intrigue without alienating," says Sonnet.
It's a tall order – but an increasing number of dramas are managing to pull it off.