The restoration of the Ghent Altarpiece shows the enduring allure of Jan van Eyck

The mystery of the most stolen painting in history has captured audiences and scholars for centuries. Its latest restoration shows that a Van Eyck isn’t just a work of art, writes William Cook, it’s a time machine

The Van Eyck brothers’ body of work gives incredible insight into medieval religious thinking, as well as documenting the changing nature of oil painting (The National Gallery)

I’m standing in a twilit room in Ghent’s Museum of Fine Arts, watching the meticulous restoration of one of the most magnificent artworks of all time. In the new year, the Adoration of the Mystic Lamb will be returned to St Bavo’s Cathedral here in Ghent (its home, off and on, for the past six centuries) but in the meantime, anyone is welcome to come and witness this painstaking restoration process as it happens. Stripped of its dull layers of varnish and its countless clumsy alterations, this medieval masterpiece has never looked so vibrant, so alive. For the first time in centuries, you’re seeing it the way the Van Eyck brothers painted it. And what an amazing painting it is!

Standing alongside me is Helene Dubois. She first saw this painting as a schoolgirl, nearly 40 years ago. It inspired her to become an art restorer. “Seeing it up close was an incredible experience,” she tells me. Now, half a lifetime later, she’s in charge of this project, the culmination of her life’s work so far. Talking to her, it’s clear this is an emotional assignment. So why does this painting inspire such reverence, such devotion? Why do so many people get so excited about the Adoration of the Mystic Lamb?

Ever since it was first unveiled in St Bavo’s Cathedral in 1432, the Adoration of the Mystic Lamb has been an endless source of fascination – an obsession fuelled by the enduring riddle of what on earth it might mean. Six hundred years since its creation, scholars are still squabbling about the symbolism of its imagery, but it’s generally agreed that, broadly speaking, it’s a depiction of the apocalypse – the end of the world as described in the Book of Revelation. The main panel depicts Jesus Christ, transformed into the Lamb of God, surrounded by all the people he’s decided to save on Judgement Day. It’s an insight into the medieval mind, a medieval view of heaven.