And then there's the portrait by Harold Knight of the English impressionist Alfred James Munnings, to be offered at Christie's in London on December 16 with an estimate of £30,000-£50,000.

Painted in 1910, it was discovered on a canvas hidden beneath Carnaval, a work completed some five years later by Harold Knight's more celebrated wife, Laura.

Ironically, that goes in with a lesser £20,000-£30,000 estimate. But what this story reminds us of, most of all, is the fact that art is produced by warm and often hot-blooded humans.

We have no idea why a man's serious and important work of art should have been covered by a less personally involving painting by his wife. But it opens the way to a welter of speculation.

It was during a detailed examination of Carnaval that Rooth noted that at the back there appeared to be the edges of two stretched canvases. Removing the 83 nails that pinned down Laura Knight's work, he glimpsed a flash of rich and almost luminous green brushstrokes.

And what he was left with was Sir Alfred James Munnings Reading, a highly important early portrait of the painter seated in a garden chair.

"I could barely believe my eyes," he says. "The intensity and freshness of the colours, uncovered for the first time in almost a century, took my breath away.

"Was the portrait by Laura Knight? Why was such a beautiful and important work hidden so deliberately? I began my research of a painting which I believe encapsulates the intrigue, romance and complexity at the heart of the community of British impressionists working in Lamorna, Cornwall, at the beginning of the 20th Century." Research has revealed that the painting relates closely to The Sonnet, a lost work by Harold Knight which was exhibited at the Royal Academy in 1911. The existence of a preparatory portrait by Harold of Florence Carter-Wood, who is amongst the group depicted in The Sonnet, gives credence to the theory that this picture is also by him.

The Sonnet shows a larger scene with the charismatic young Munnings seen as in the newly discovered portrait, delivering one of his frequent dramatic readings to a group of young ladies including his future wife Florence and Laura Knight. There seems an element of gentle satire in Harold's portrayal of Munnings' declamatory gesture.

The fact was that the atmosphere among the artists at Lamorna was fuelled by passion and fraught with emotional tension, not least in the complex relationship between Munnings and the Knights.

The reserved Harold saw Munnings as a flamboyant extrovert, and his wife's admiration of the other man caused him great concern. Then the group was thrown into another level of turmoil when Florence Munnings committed suicide in 1914.

Did Harold dispose of the painting and Laura rescue and hide it? Did one or other choose to obscure it after Flora's death, maybe blaming Munnings for being absent in his wife's hour of need?

Who knows? But this is a remarkable find that gives us a glimpse of a tangled human tale.