The discovery of Lady Jane - rolled up under the table

Christopher Johnstone. Photo / Supplied

In 1973, Christopher Johnstone was a junior curator of the British Collection in what was then the Tate Gallery, these days known as Tate Britain. Johnstone, who later became director of the Auckland Art Gallery, was working on his first book, about the 19th century British painter John Martin.

"I knew that one of John Martin's paintings had been in the National Gallery collection in the Tate, The Destruction of Herculaneum and Pompeii, but it had been destroyed or lost in the great flood of London in 1928," says Johnstone.

With flood water pouring into the Tate's basement, reaching a height of nearly 3m, many works had been lost or damaged, including some by Martin's contemporary, the great artist J.M.W. Turner. But the Tate's records were in some cases incorrect.

"I was in conservation one day," recalls Johnstone, "and I said, 'What's that? It looks like a Turner.' My colleague said it was one of the Turners damaged in the flood which they used for interns to practice on to see if we can get it back into reasonable shape. Suddenly, it occurred to me that if there were Turners that survived, other things might have, including the John Martin work I was looking for.

"I asked them, 'What were all these rolls of canvas under the big table?' They said they hadn't been looked at since the flood. I said, 'Hold on - the John Martin could be there. What about if we measured up any of the rolled canvases that were big enough to hold the John Martin?' There were only two or three candidates.

"Then I got a call from the office to come down - they'd found the John Martin. I went down and there it was, in a terrible mess, but the most extraordinary thing was that the painting had been rolled up with the Delaroche, The Execution of Lady Jane Grey.

"It was an extraordinary moment because on the one hand I was incredibly disappointed that what I was looking for was not worth pursuing at all and on the other hand, this extraordinary 1830s work was in virtually pristine condition.

"My excitement over the discovery of the Delaroche was tempered by my disappointment with the Martin. Although I was writing a book about a rather conservative but important 19th century painter, my interests were wide and far-reaching. I wasn't terribly interested in a French historical painting so I didn't think too much about it."

Johnstone's book on John Martin was published in 1974. Three decades on, he is fundraising manager for the Auckland Philharmonia Orchestra and the author of several books including, most recently, The Painted Garden in New Zealand and Landscape Paintings of New Zealand. His name also lives on in the National Gallery catalogue notes for The Execution of Lady Jane Grey, painted in 1833, lost in 1928, rediscovered in 1973 and today the gallery's best-selling postcard.