The beauty of the battleaxe

They are sensible hats, brown and beret-style, certainly not Sunday best. Bought somewhere in Bolton, Patricia Routledge wears them jammed down, as if to keep the lid on her equally sensible hair-do. It's all plain as plain can be, and though a far cry from the ornate floral do- da's favoured by a certain Mrs Bucket (altogether: "It's pronounced Bouquet"), Hetty Wainthropp's hats call attention to themselves, too. If Hyacinth's headgear runs the gamut of intimidating and self-deluding, Hetty's proudly proclaim her down-to-earth northern roots, her working-class respectability.

They are also a lie. While sensible hats are what you'd expect from a 60-year-old pensioner living on the interest from her husband's redundancy pay-off, they are not entirely suitable for Britain's hottest TV detective (even Miss Marple dresses to her station, and so does Jessica Fletcher, older but stylish star of Murder She Wrote). Those berets are camouflage - they are there not to cover her scalp but to hide her surprisingly fevered grey cells. As Hetty boasts - it's becoming her catchphrase - "I'm a mistress of disguise."

She isn't, of course. Hetty, as her creator David Cook acknowledges, is in an instantly recognisable mould - the Great British battle-axe, part Peggy Mount, part Nora Batty, with a dash of Violet Carson. We know her (or believe we do). And we'll be getting to know her much better, because Hetty is entering the culture, and entering it fast.

Who is Hetty Wainthropp? Check out the cover story of this week's Radio Times, which she adorns handbag on arm, gloves in hand. Or do what 11 million-plus viewers have been doing the past four weeks and tune in to BBC1 on Wednesday nights at 9.30pm and catch Hetty Wainthropp Investigates.

It's a strange, and strangely addictive experience, not to mention one of the BBC's increasingly rare instant hits in popular drama. Indeed, you could feel the blend of familiar formula, ordinary life and... something else - kick in a mere three minutes into the debut episode. Our gruff heroine sits up in bed on the morning of her 60th birthday, opens a card, announces she's not about to drift into old age, has a wee weep while reading her husband's Hallmark purchase, and breaks into a boiled egg. Fairly brisk, standard scene and character setting, except that inexplicable whatever that hooks the attention is already at work, irrespective of the plot or acting. And Hetty hasn't yet met Geoffrey, her 17-year-old sidekick (Dominic Monaghan), hasn't turned sleuth, hasn't found the bag lady's body, hasn't been the victim of attempted murder: "I fell through the hole in that ceiling," she remarks, gruffly. "It's no laughing matter."

Indeed not. There are those who find Hetty's lightening acceptance no laughing matter either. One ITV head of drama, who'd rather not be named, thank you, can barely be restrained: "What have you got here? Pat [Routledge] is excellent but it's cosy, twee and fake. There's also too much plot and not enough time. The stuff I've seen has been in a rush to get finished, like it's been cut down. And the cliches... Outside of Last of the Summer Wine have you ever heard anyone use the expression 'cheeky monkey'?"

No. But would he grab the series if it were available? "Ha ha... Absolutely."

"ITV did turn Hetty down," says Cook, who also co-writes the series with John Bowen, and whose book Missing Persons first introduced the character. "We made a two-hour film for Yorkshire TV with Patricia, back in 1988 I think, and it went over well. She played Hetty as a 70-year-old in a pink jumpsuit." Cook pauses, savours the image, continues. "Yorkshire commissioned scripts. It was going to be like Morse; two-hour films. Then word came down from Flexipool: 'Too pipe and slippers for us.' "

Pipe and slippers may be the mysterious key to the series' success - why should Hetty Wainthropp Investigates work when, say, the wacky detective series Moon and Co, didn't? Or perhaps it is simply the presence of Routledge, as the producer Carol Parks insists. Hetty, she points out, enjoys star insurance, a guarantee most drama series today demand: "The figures are down to Patricia. After Keeping Up Appearances she has a huge audience. They turn on for Patricia. They adore Patricia. She can, thank heavens, actually make viewers sample."

The actress and the role merge splendidly. As Parks observes, Hetty instantly disposes of Hyacinth. But, even so, this is only scratching the surface of something... what did the ITV boss say? Something cosy, twee, fake.

Hardly. Hetty's surface blandness - no nudity, little violence and minimal bad language - is deceptive ("I'm a mistress of disguise"). Formula hides the unexpected; a social conscience, a campaigning streak, wholly absent from the airless worlds of Marple and Fletcher.

Take Hetty herself. She may personify the Great British battleaxe but, unlike her pre-decessors, her strength is challenged. Peggy Mount didn't fear being "put on the scrap heap". Hetty does. She dreads becoming that most misunderstood of minorities: batty old lady. Yet, by becoming a detective, she becomes a batty old lady - on her own terms.

Hetty's situation is mirrored by the adolescent Geoff's, stuck on a supermarket cash till, shoplifting for kicks, until Hetty shares her own sense of purpose: "I don't hold with despair." Hetty and Geoff naturally empathise with those shoved to the margins of the mainstream. The homeless featured heavily in the first episode, a deaf mute in the second, and tonight's penultimate programme - "hard hitting", promises Carol Parks - revolves around a missing schizophrenic.

This is hardly surprising when one learns that David Cook's previous quietly but implicitly political work has tackled brain damage, the autistic and the handicapped (he wrote the highly regarded Walter for Channel 4). Hetty seems to share Cook's general mistrust of authority (odd in a genre where authority often represents the status quo). She's unshaken by the notion that a chemical plant is leaking hormones into the water supply, barely bats an eyelash at the notion that a policeman could have kidnapped the aforementioned deaf mute, and finds the idea that robbing corpses disgusting but plausible.

"Firm but gentle" - Cook's description - Hetty is the very model of a permissive mother, the maternal figure we secretly wish for; all seeing and all knowing (it's telling that she treats husband Robert as much as a child as she treats Geoffrey as an adult). Perhaps this is why Hetty can tackle tricky subject matter without offending her target audience. Carol Parks's post-bag bulges with letters praising a programme: "I'm not ashamed to watch with the entire family", says one, in reaction to a storyline about a sexually abused beauty queen with a paradoxical liking and loathing for rough sex. "Hetty doesn't understand that," explains David Cook. "In an earlier draft she actually says she can't imagine sex hurting and what is the world coming to? And Geoff says, 'We might have to get used to it.' Hetty might change in the future. What she experiences may make her retreat, become a bit reactionary."

Arguably, it's Hetty's learning curve that, so far, gives the series sub-text, that flipside of formula that every popular drama must have to win the public's mind - and heart.

"She's no Dalgleish," says Parks. "Give her forensic evidence and she'd be flummoxed." (Luckily there's a tame police inspector on hand to handle such details.) "But Hetty knows people. That's what is important. And people feel they know her."

Which is why the lady ought to be left alone. The series isn't perfect, but the popular isn't required to be. Only compulsive.

Cook laughs: "Ah, well, the powers that be are already going on about making the second series quicker, slicker, like a 'proper detective series'."

The voice of authority. Imagine Hetty's reaction to that.

"I know, I know. But I've told them Hetty is not really a 60-year-old investigating detective. She's a 60-year-old investigating life."

n 'Hetty Wainthropp Investigates' is on Wednesdays, BBC1 at 9.30pm to 7 Feb