In 1425, at Domrémy in eastern France, a young girl aged only 13 heard an ethereal "voice". It told her to lead an army to defeat the dastardly English invaders, allowing the French dauphin to become true King of France.
This was no small order for an illiterate country lass called Joan d'Arc. But the rest, as they say, is history. To Joan, her "voice" was confirmation she had God on her side, and by God she pulled it off, even though it cost her a grisly death.
Ever since, she's been known as the Maid of Orléans - the scene of her first victory.
No one told Joan that it was not really the done thing for a nobody kid to front the ruler of her country, tell him that he was a pussy, and if he was not up to ousting the English then give her the army to do the job herself.
Young Greta Thunberg's story so far is barely less astounding. A quiet Stockholm lass aged 15 bunks school and parks herself outside the Swedish parliament because an idiot world needs someone to tell its governments to stop the suicidal carbon-emitting practices threatening its very survival. And if no one else will, well, then she will.
Greta wasn't looking to lead an army – she just couldn't understand why there wasn't one already, fighting the monumental human rapacity and apathy that's allowed a cataclysm-in-waiting to increasingly endanger the planet.
There are startling other similarities between the two young maids. They both personify formidable self-confidence in their respective causes - an unshakeable sense of rightness, not to be diverted or dissembled.
Both also astounded observers by the maturity with which they addressed and argued their cause against seasoned vested interest members of the powers-that-be. In Joan's case, we only have contemporary accounts as to her single-minded resolve. But with Greta, we see it for ourselves in real time media reports.
Both girls also eschewed overtly "feminine" attire or adornments.
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Greta brings to mind the implacable searching Cyclopean eyes of the Martian invaders in H G Wells' classic, War of the Worlds, where Martian machines roam the devastated landscape looking for survivors. At any sign of human life, a baleful beam from an elevated control pod inscrutably swings to pin-point the target and deliver an unerring death zap.
Greta's stare is in the same league. Inscrutable-on-a-stick. Popes, presidents, prime ministers, corporate nabobs and tech tycoons – no matter. They all get the glare and third degree. The sole exception would possibly be Donald Trump. To her, Trump's epic climate change denial is so far beneath contempt that he's not worth the wattage.
Last week, Greta's gimlet eye also swung to catch like a bunny in the headlights everybody's good guy and seeming Mr Squeaky Clean - gasp! - Roger Federer himself. The Apollo of the tennis courts crumpled like an ant under a sun-fuelled magnifying glass as Greta's Truth-Ray glare exposed the fact that Federer's main sponsor – as if he needs one! – Credit Suisse, is donkey-deep in fossil fuel investments.
With Greta's bee now buzzing in his bonnet, Federer's concentration will be hard pushed to add the 2020 Australian Open to his Slam triumphs – particularly with smoke from apocalyptic bushfires curling over the Melbourne courts.
Some say Greta's single-mindedness is a symptom of the Asperger's Syndrome she apparently has. If so, it's a condition everyone should have. This courageous young woman has raised more than the morale of a medieval French army – she's galvanised an entire global population of recruits now fighting for future human life on the planet against naysaying and stonewalling governments.
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That includes ours, which – despite the greenwash – is hypocritically as donkey deep as Credit Suisse in business as usual, with an Opposition tragically even more so.
Greta's withering gimlet eye and uncompromising stance are beacons in the battle against our self-created planetary arch enemy. She does Joan honour.