Ernest Shackleton's granddaughter, Alexandra, refused to tell Ryan Tubridy her best joke because, she said, she’s only just met him. She also doesn’t like telling the joke to children because they won’t understand it. So the only way we might get to hear her best joke is if we tune in to a new TV documentary about her grandfather, Shackleton’s Cabin, on RTÉ One next Monday, 2 May.

The cabin in which Kildare’s most famous explorer took his last breath was donated to the Shackleton Museum in the Athy Heritage Centre in 2015, where it forms part of the permanent exhibition. The cabin was originally part of a ship called Quest, which Shackleton used on his final voyage. Alexandra explained its origins:

"Well, the cabin is from my grandfather’s last ship, Quest, which, as you said, he died in, a hundred years ago this year and I last saw it when it on its own in an open-air museum in Norway. After lots of tribulations it came here to a very good place. It’ll be at the Ernest Shackleton museum, which will be the first dedicated museum in the world."

But why was the cabin in Norway in the first place and how did it come about that it moved to Athy? It’s a long, complicated story (one that might need a documentary to tell it properly) and Alexandra told Ryan that she didn’t know all the details:

"As you know, Ernest Shackleton was very young when he died – he was only 47. And the last entry in his diary, when they’d just got to South Georgia, he said, 'In the glimmering twilight, a lone star hovers, gem-like above the bay.’ A few minutes later he was dead."

Of course, Shackleton’s most famous ship was the Endurance, the wreck of which was recently found more than 3000m under water, 107 years after she sank.

"When it became apparent that the ship – after living for months on the ice – that the ship was never going to take them home, my grandfather wrote, ‘A man must set himself to a new mark, directly the old one goes.’ And his new mark was to bring every member of the expedition home alive, which he did."

The discovery of the wreck of the Endurance was a surprise to Alexandra because, as she put it, most people have seen footage of ships being crushed to bits before sinking under the ice and there was never any reason to expect that the Endurance’s fate would be any different.

"Everyone knew she was Titanic depth – 3,000 metres, far too deep for human beings – and I thought, a lot of people thought, she would just be a pile of spars, but the little wood-eating creepy – 'cause the ship was wood – doesn't live there. And the ship looks so wonderful and beautiful and shiny because apparently a useful jellyfish lives there and the jellyfish likes eating algae and so it kept the ship clean. But I never thought there’d be so much left of her."

Then comes the surprising – not to mention dramatic – admission from Alexandra: "You know she belongs to me, the ship?" Ryan asks her to explain that claim and Alexandra is happy to oblige:

"Grandfather insured the ship and so when it was crushed it reverted to the insurance companies and it was discussed with the insurance companies and they handed over their interest to myself and my first cousin."

So you’ll have to get Alexandra’s permission if you want to take a submersible down to pay the Endurance a visit. Except that’s something you can’t do (even if you had a submersible handy) because the wreck is designated as a protected historic site and monument under the Antarctic Treaty System. As the co-owner of the Endurance, Alexandra is happy for people to look at her and take pictures, but she doesn’t want anyone boarding her or searching for memorabilia:

"She should be left just as she was. Looking, yes. Touching, no."

Alexandra never knew her grandfather, but she learned all about him from her grandmother Emily. Unsurprisingly, as an explorer, Ernest was a restless soul who spent a lot time away from his family doing his, you know, exploring. But it was quite normal at the time for men to spend long periods away from their families. Alexandra summed up her grandfather nicely:

"I don’t think he was perfect. I think he was a very great man. Some people, if they’re related to somebody well-known, behave as if they’re a saint. He wasn’t a saint, he was a very great man and a very great leader. I’m very proud of things – he wrote poetry, the only Antarctic explorer who wrote poetry. But he was also an incredibly practical man who would do any job on an expedition, however menial. A hundred years ago, that was very unusual."

You can hear Ryan’s full conversation with Alexandra Shackleton by going here.

Shackleton’s Cabin can be seen on RTÉ One and the RTÉ Player on Monday 2 May at 6.30pm.