Does Gillian Duffy exist? The question is not as foolish or frivolous as it may seem. If you wanted to invent a character that the right-wing popular newspapers would wish Gordon Brown to insult as "bigoted" after a conversation that covered immigration and taxation, you could hardly do better than Duffy. Indeed, the Daily Mail's Stephen Glover admitted that she might have been "picked out by divine providence". Nor could the timing have been better. The only story of the campaign until Duffy's appearance involved three men in suits standing in a television studio. There had been no gaffes, no shouting matches, no fisticuffs. On the morning of Brown's Rochdale disaster, the Sun was reduced to splashing on a cartoon pig that hadn't joined a Labour policy launch.

Clearly, somebody called Gillian Duffy does exist and some facts about her are verifiable. She is a woman of mature years with a Lancashire accent and what used to be called a comfortable figure. She is also a grandmother, and "grannies" hold a special place in tabloid esteem, alongside war heroes and murder victims. We have been told many other things about her lifestyle, family, home, career and political beliefs. These created a "profile" (some newspapers headed articles with that very word) of a woman who can be described as "salt of the earth" (Trevor Kavanagh, the Sun), "honest as an Eccles cake" (Benedict Brogan, Daily Telegraph), "a decent, moderate, sensible person" (Glover again), a "redoubtable matriarch" (Janice Turner, the Times) and, in what must be record time, "a national treasure" (Chris Roycroft-Davis, Daily Express).

Wheelie wonderful woman

My question mark concerns this Gillian Duffy, as elaborated by mostly right-wing journalists. How much of what the press told us was strictly factual, and how much, if not exactly invented, the result of hopeful deduction and speculation? Duffy, we were told, is aged 65 or 66 (often, writers in the same paper couldn't agree) and had stepped out from her terraced house, wearing "her best coat", and "tottered off to the shops" to buy bread and (according to the Telegraph) milk, too. She lacked, the Mail's Quentin Letts regretfully reported, "a wheelie shopping trolley".

Now retired, she used to be a council worker who "helped" disabled children (the Telegraph, describing her as a "transport escort", was most specific) and treated them with "compassion". Her father, Walter Bond, was a window cleaner who sang "The Red Flag" in Manchester's Free Trade Hall. She "lovingly . . . cared for" her husband, a painter and decorator, as he died of cancer. Let me allow the Express's Roycroft-Davis, a former Cameron speechwriter, to complete the picture. "You just know her spotlessly kept house has pictures of them [the grandchildren] everywhere, alongside the treasured photo of her late husband that holds pride of place . . . I'm prepared to bet Mrs Duffy doesn't have a credit card in her purse. That's because she was brought up to believe that if you want something you work for it and save for it."

The right-wing, populist press thus fleshed out a character that represents its image of what a sixtysomething, working-class Briton should be like. Max Weber described how social scientists create an "ideal type" (a technical term, not intended to imply perfection) from "a great many diffuse, discrete, more or less present and occasionally absent concrete individual phenomena", in order to make sense of reality. That is not how the Sun would put it, but you get Weber's drift. A similar exchange could have taken place between Brown and a 19-year-old tattooed youth, but creating an "ideal type" would have been more difficult.

If any paper was likely to challenge the Duffy image, it was the Daily Mirror, which is now the only Labour-supporting national daily. Perhaps it could reveal that Duffy was a Tory plant, parachuted into Rochdale from an aristocratic estate (preferably owned by a distant cousin of David Cameron's), where she had served in the kitchens, deferentially and faithfully, for decades.

I don't doubt that if anyone had quizzed Cameron about gay rights and the Tory leader had later muttered about "that poofter", the Sun would, by now, have exposed the questioner as a serial child abuser. Alas, the best the Mirror could manage was a suggestion that Brown thought Duffy had asked where eastern European migrants were (I here use the tabloid newspaper style) "f***ing from", not: "Where are they flocking from?" Slightly more impressive, if unconvincingly sourced, was the People's story that Duffy wasn't, as the narrative had it, about to send off her postal vote for Brown; rather, she had lost the voting slip.

Media creation

You may object that most details about Duffy were corroborated by the Mail on Sunday, which, thanks to its deep pockets and the good offices of Bell Pottinger (even salt-of-the-earth Rochdale grannies need PR companies), won an exclusive interview. But by that stage Duffy would have been saying what was expected of her, and the journalist hearing what she expected to hear. Only a few, faintly discordant notes were allowed to creep in: the Duffys paid private school fees, albeit for just three years, and Walter Duffy was secretary for the local branch of the Federation for Window Cleaners, which is not, as implied, a union, but an employers' trade association.

Let me, as politicians say, be clear. I do not accuse anybody, least of all Duffy, of falsehood. For all I know, everything we have been told about her is true. I merely point out that, within a few hours, the media reduced a woman's life and personality to what was little more than a caricature. Duffy was brave to challenge Brown. It would have been even braver of her to challenge the reality the media created.

Peter Wilby was editor of the New Statesman from 1998-2005