William Shakespeare left behind 37 plays, 154 sonnets, a few precious facts about his life and not one single image that can be said, with certainty, to be the man himself.

Successive generations have wondered what it would be like to look into the eyes — the “windows to the soul” — of the world's greatest writer. Yet Shakespeare's face is, and probably always will be, elusive.

The Cobbe portrait has a strong claim to be the only known image of Shakespeare painted from life, but we will never be certain. Before its discovery, only two images of Shakespeare were widely accepted as credible likenesses, both created after his death in 1616 — the engraving by Martin Droeshout the younger that appeared in the frontispiece to the First Folio in 1623 and the funerary bust at Stratford-upon-Avon, supposedly based on his death mask and installed in 1623.

These images were endlessly reproduced, creating the familiar stereotype — high forehead, pointy beard and a ruff. Many found the somewhat dour, elderly image of Shakespeare, with bagged eyes and receding hairline, hard to reconcile with the joyful author of genius.

The Droeshout Shakespeare was approved as a near likeness by his peer, Ben Jonson, yet Mark Twain described it as “bladder-faced”. The monument on Shakespeare's tomb in Stratford has been compared with that of a “self-satisfied pork butcher”.

In the Cobbe portrait we find a different image: the eyes sparkle in a fresh face, meeting the viewer with an expression that seems quizzical, poised and refined. The lips carry just the hint of a smile. The Shakespeare in this portrait is supposed to be in his 40s, yet he still has a full head of hair, and no hint of grey in his beard. His hair appears auburn in colour, dovetailing with contemporary accounts.

But maybe flattery was the aim; ironing out the wrinkles and marks of age, for this is undoubtedly intended to be a celebratory image, the Jacobean equivalent of a publicity photo.

The artist's subject is clearly wealthy and successful, clad in gorgeous embroidered doublet with decorative braid and elaborate lace ruff — a significant (and expensive) mark of social standing. As Shakespeare himself opined: “The apparel oft proclaims the man.”

Over the centuries, numerous paintings have been put forward as life portraits of Shakespeare, but none has been generally accepted as the real thing. Six of the most famous were gathered in 2006 for an exhibition at the National Portrait Gallery, entitled Searching for Shakespeare.

The centrepiece was the so-called Chandos portrait (named after a previous owner), the first picture presented to the National Portrait Gallery in 1856. Attributed to a little-known artist named John Taylor, that image depicted a bohemian figure, rakishly dressed in open collar with loose ties. In his ear hangs a hooped earring, a fashionable accoutrement for actors of the day. Some Victorians recoiled at the idea that the Chandos portrait represented Shakespeare. One critic, J. Hain Friswell, insisted “one cannot readily imagine our essentially English Shakespeare to have been a dark, heavy man, with a foreign expression”.

The Cobbe portrait has been dated in or around 1610: if that date is correct, Shakespeare would have been 46 when he sat for it. The son of a glove-maker, Shakespeare came from relatively humble stock, yet the image depicted here is of a rich man, kitted out in a sumptuous outfit that would have cost, at today's prices, well over £7,000. But there is something about the sitter's wry expression that suggests he knows he is dressed up to play a part, and that all the world's a stage.

Shakespeare's contemporary John Aubrey described him as a “handsome, well shap't man”, a description that fits this portrait far better then the dumpy, ill-shaven, slightly weary-looking writer bequeathed by Droeshout.

The Cobbe portrait may fit our mental image of Shakespeare, but without evidence in the form of a written commission, it will probably never be definitively authenticated. The painter not only did not append his own name to his work, but also failed to identify the sitter, as did every one of those who subsequently copied it.

Whatever the truth, the mystery surrounding Shakespeare and his life is part of his allure. Just as the relative paucity of facts about his life has led to speculation about his authorship of such a prodigious body of work, so the lack of verifiable pictures has prompted numerous claims to have “discovered” the missing portrait.

The Greeks invented an imaginary image of Homer to render the poet more accessible, and for four centuries admirers of Shakespeare have imagined his face, based on the most meagre of historical clues. Now we have another image to add to the collection, and a most beguiling and persuasive one. Shakespeare wrote sublime poetry, suffused with wit, joy and passion. The face of the man in this portrait has depth, delight and a little devilry.

Even if it is not the face of Shakespeare, it is surely the sort of face Shakespeare deserves.

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