In a week's time, Christie's, the London auction house, expects a bumper response to one of its sales, despite the apparently unappealing nature of much of the material on offer. It seems difficult to imagine, for example, who would be interested in an old menu card, especially one carrying an estimated price of £1,000-£2,000 sterling. And who might want to pay the same for two six-inch splinters of wood?

The explanation is that they are not simply splinters, of course, but fragments from a sledge used by Sir Ernest Shackleton on his Antarctic expedition of 1907-09, while the menu comes from his last dinner in the region some years earlier. They are just two lots from about 100 items of Shackleton memorabilia being offered by Christie's at a time when the popularity of the long-deceased polar explorer is growing ever greater.

Born at Kilkea House, in Co Kildare, in February 1874, Shackleton was a member of an Irish Quaker family. When he was 10, he and his immediate family moved to England, but he would return to Ireland in later life to lecture on his travels.

He achieved considerable fame during his lifetime, but following a relatively early demise - he died from a heart attack 10 days before his 48th birthday - his reputation tended to be overshadowed by that of Capt Robert Scott, who famously perished in 1912 while attempting to return from the South Pole.

The resurgence of interest in Shackleton's life and achievements originated largely in the United States, where, curiously, he is considered a role model for leadership in the business world and is cited in best-selling management books.

Last year, Michael Smith's biography of the Kerry man Tom Crean, one of Shackleton's companions in the Antarctic, sold about 20,000 copies in the Republic. At the same time, a number of biographies of Shackleton have also appeared, and he is about to be the subject of two films: a four-part Channel 4 series due for screening early next year, with a cast led by Kenneth Branagh; and a $40 million Hollywood production directed by Wolfgang Petersen, who made A Perfect Storm and Air Force One, and starring Russell Crowe.

The Shackleton craze is being observed with quiet pleasure by Jonathan Shackleton, a second cousin who lives in Co Cavan. The unofficial family historian, he plans to publish a book on his famous relation next year, having lectured around the world on the subject since the early 1980s.

Jonathan Shackleton traces his interest in the explorer to his childhood, when an aunt gave him a copy of the first biography. "It complemented my interest in the family anyway," he explains, "and then I realised that no one much in Ireland or Britain really knew about Shackleton and his Irish connections."

Twenty years ago, Jonathan Shackleton studied for a masters' degree from the Institute of Polar Studies at Ohio State University. While there, he agreed to give a lecture on the explorer. "It was a brown-bag talk - during lunchtime - and I thought just a handful of people would turn up; in fact, the place was packed."

Since then, Shackleton, who used to teach biology and natural science at Mount Temple school in Dublin, has found more and more of his time taken up attending events associated with polar exploration, at which he is regularly invited to give talks.

Jonathan Shackleton enormously admires the polar explorer, as much for his strength of character as for his heroic exploits. He believes Ernest Shackleton's Irish and Quaker heritage was crucial in moulding the man. "He never told lies, never dissembled, never said anything he didn't want or need to say."

Jonathan Shackleton argues that the explorer's maverick status, working outside the Establishment Royal Geographical Society, can also be traced to his Irish family and upbringing.

Having spent so much time investigating Ernest Shackleton's career, he finally felt obliged to travel to the Antarctic, which he has visited six times during the past 18 months. "One of my most moving experiences was visiting his grave on South Georgia. It's just a rough-cut granite headstone, giving his dates of birth and death, but it stands against a background of fantastic snow-covered mountains, surrounded by the tombs of Norwegian whalers who used to live in a station there."

At the end of the year, he will be back in the Antarctic, leading a group of six teenagers from Drogheda, the first students from Europe to visit the area. "They're still looking for funds, but I think it will happen and be the most extraordinary occasion for everyone."

Meanwhile, over the last weekend of October, he is speaking at the first weekend conference dedicated to Shackleton, in Athy, Co Kildare, where he has lent the local heritage centre a sledge used during the explorer's 1907-1909 "Nimrod" trip.

So why does Jonathan Shackleton think that a man who died almost 80 years ago, and who, on his most famous trip to the Antarctic, in 1914-1916, had to turn back before reaching his goal, should be considered so inspirational?

"I actually have a passion about him which I think rubs off on other people. And having been where he was, I've got a very real idea of what it was like and what he went through. Anybody who gets to learn about Shackleton wants to know more and has an almost unqualified admiration for him."

Also, he says, it is possible to understand why, despite the apparent failure of Shackleton's 1914-1916 expedition, he should be held in such high esteem in the business environment.

"Of course, it's different in the corporate world: they may be under a lot of mental pressure, but they're not going to die. Shackleton provided very great leadership in extreme conditions. It's an inspiring tale, although a lot of what he did was straight common sense. These men's lives were on the line and he kept them together."

Finally, it is worth noting the observation of a transatlantic admirer who two years ago remarked that Shackleton and his team were old-fashioned heroes, "trying to subsist in one of the last irony-free zones of the 20th century".

Given the growing interest in polar explorations, it seems highly unlikely that Jonathan Shackleton will be able to buy any of the material on sale at Christie's. It was originally owned by the explorer's daughter Cecily, who left it to a distant relation; it is being sold so that even more important memorabilia may be preserved at the Scott Polar Research Institute, in Cambridge, where a Shackleton Memorial Library has been created.

Jonathan Shackleton expects American enthusiasts to be the most ardent purchasers at next Tuesday's auction; inevitably, their presence will affect prices. While this may be personally disappointing, his concern rests primarily in developing a greater global awareness of Shackleton's Irish origins. As the final line of Jonathan Shackleton's curriculum vitae notes, he is "prepared to lecture on Antarctic history anywhere in the world".

The Polar Sale is at Christie's, London, on Tuesday, September 25th. Further information from 00-44-20-73892057, or see www.christies.com