Matthew Norman: Margaret Thatcher is still big, it's the politicians that got small

The timing of the release of 'The Iron Lady' has a resonance that transcends normal critical criteria

With the Iron Lady, now as ever, there are no two ways about it. You simply have to see the Margaret Thatcher biopic when it hits the big screen in January. More than that, you must drag along your children if, as with our pubescent boy, the name of Thatcher is but the faintest echo on the breeze of recent history.

We have tried to give him a flavour, but no one under 40 can appreciate the magnitude of her dominion over us between and beyond the years 1979-1990. If Meryl Streep comes close to doing that, there will no prizes for guessing which two words will follow "And the Oscar goes to..." in March.

It is a mark of Lady Thatcher's undying epicity that her genius for igniting contention and polarising her former subjects endures even now. Some eight weeks before its release date, her supporters, upset that the film touches on her dementia, are lining up to knock it down.

"I can't be bothered to sensationalise this rubbish," harrumphs Tim Bell, the advertising man she sponsored when – as befits someone who has never denied claims of cocaine use in his past, and who had a conviction for a spot of solo delicto in plain sight of au pair girls passing his Hampstead Heath home – he took his place in the House of Lords. "It is a non-event."

His lordship's delicately nuanced critique comes from a standpoint of absolute ignorance. Those who have seen the film suggest that it is not "a left-wing fantasy", as other unnamed Thatcher friends and relatives are quoted as saying, but well balanced and far from unsympathetic. But if the Thatcherophile right judges it a vicious hatchet job, and the Thatcherophobic left as a slavish panegyric, this will do her, if not it, some justice. "One of us or against us" was always the motto, beneath the handbag rampant and the sunken Belgrano impaled, on her heraldic crest.

Whatever the dramatic merits of Streep's performance, Phyllida Lloyd's direction of The Iron Lady and Abi Morgan's script, the film's timing has a resonance that transcends conventional critical criteria. The oddity, in an age when the process of revisionism runs virtually concurrently with the history itself, is that it took so long. Although there have been many plays, including Ian Curteis's admiring The Falklands Conflict, in which Patricia Hodge played Thatcher as sexy and sardonic, this is the first motion picture.

By way of some weirdly inverted temporal paradox, Mr Tony Blair has already starred in several. He may have been PM for almost as long as her, but you'd have to be barmy to regard him as a historic figure in anything like her league. Our son, three weeks old when he came to power, was 10 when he left, and Blair meant very little to him.

Thatcher on the other hand... Suffice it to record that in May 1989, to mark her decade as PM, a colleague and I tried to illustrate her impact by taking two children born the day she came to power to Downing Street. Frankie belonged to a family rendered horribly deprived under her rule, all of them living with perpetual bronchitis in a damp-ridden home on a tragically decayed Sunderland council estate. Gemma's family in the Thatcherian stronghold of Essex, from a similar 1979 financial starting point as Frankie's, had risen to join the gold-card, two-car classes, and could afford a pony for their little girl.

It pays testament to what Mrs Thatcher meant to 10-year-olds, from north and south, east and west, back then that at the first distant click of court shoes from within that deep house, blood gushed from Gemma's nose and Frankie rushed to the loo to throw up. The tiny sparrowhawk of a woman who eventually joined us petrified me, too. I don't recall admiring the lips as Monroe-esque, but by Christ the eyes were Caliguloid.

Twenty-two years later, what makes this film so poignantly timed isn't merely the renaissance of Europe as the hottest of political potatoes, or how some will regard the financial cataclysm, in part at least, as the blossoming of the tree she planted by liberating the City with her Big Bang. It is the contrast between Thatcher's metaphorical size and that of her impersonators.

Blair, who wanted to be her, was no more than a parody... a ghostly opportunist forced, by his Iraqi adventure, to pose as a reverse gear-free conviction politician in her mould. Cameron, who longingly hankers after Blair's electoral magic, looks like a pastiche of a pastiche. At a grand historic moment that screams out for genuine titans, we look from London to the other capitals around the world and see ersatz midgets.

Since Andrew Marr observed this in his masterly potted history of post-war Britain, it has become a cliché. But it's true that we are, all of us, Thatcher's Children now... even our own children born long after she weepily left No 10. They need to see this film. With all due disrespect to Tim Bell, there really is no alternative.