They sit together on a skinny chair, like they are welded at the hip.Helena McAlpine is locked in a deep, giddying gaze with Chris Barton, her boyfriend of 10 months, when she says: "I get scared.

"I get worried that you deserve more. That it shouldn't be so finite, that we should be able to bimble along for decades to come," she says, gently.

He laughs: "Bimble along. Yep."

It's one of McAlpine's favourite words, bimble; meaning to amble along without real aim, but in a friendly and harmless manner. Yet it's hard to conjure up a picture of McAlpine bimbling. She's in constant quick motion, chattering, laughing, doing, partying, flying planes, wrestling sharks.

Read more: Nicky Park talks with Helena McAlpine - 'I just don't want to die before I've got everything done'.

Like right now. As soon as those heart-rending words leave her lips, she's off and out the door of the cottage she's been sharing with Barton in Eden Terrace - off with Murphy the affable mongrel and a tennis ball, down to the park. It seems only a moment ago she burst in that door, grappling with almond pastries, a sadly wilting bunch of tulips, and two coffees. "I've been drinking from both of them," she tells Barton, plonking them on the table. She's also wearing his trousers.

That's unconditional love for you. And theirs is quite the unorthodox love story.

They met at a wedding in Gisborne in January. Barton knew from friends and media stories that McAlpine, livewire former music TV presenter and Auckland party girl, had terminal breast cancer. And, after a few uproarious dates, they struck a bond, which McAlpine describes as a "shout from the rooftops" kind of love.

Barton, who's 36, admits their relationship is quite unlike anything he ever imagined getting into. But he's committed to stay for the long haul. And it's likely to be a harrowing and painful haul. No one knows just how long it will be. At 35 and the mother of a 13-year-old, McAlpine certainly knows she won't be rocking on a porch watching her grandchildren; but she can't know for sure if she will see another Christmas after this one.

And yes, Barton - a tall, handsome and quietly engaging banker - knows you're going to ask the obvious question: what is he still doing here?

"I think I would be dishonest if I didn't say I don't think it all the time, almost every day. But something keeps me beside Helena," he says. "Certainly, she's given me the option to go, quite a few times actually, but in a really lovely, admirable kind of way. She says: 'You know you don't need to be here, you're a good man'. But throughout this whole relationship I've stuck by her.

"Helena and I have managed to spark something off in each other. She's a beautiful woman, but she's a beautiful person as well. I'm really attracted to her energy, her warmth and her humour." That, and her astounding personal collection of 8000 books.

Read more: Helena McAlpine joins us for a live chat.

Her humour is infectious. They giggle often, remembering all they've squeezed into their brief love story - like the almost comical, stuttering start to their courtship.

After their original encounter in Gisborne - where McAlpine lived for a while with the parents of her best friend and fellow C4 host, Clarke Gayford - they arranged to meet over banana icecream at a Ponsonby cafe on a Sunday afternoon. "She told me she knows everyone and everything that happens on Ponsonby Road, so it seemed like the right place to go on a first date," Barton says.

What she hadn't told him was the next day she was starting an intense round of chemotherapy to try to curb the secondary cancer that had spread to her bones, liver and abdominal wall.

"Helena was jacked up on some pretty heavy medication. We had a glass of rosé with our icecream, and she went a bit bonkers," Barton says. "We spent these really funny few hours, with Helena's eyes rolling back into her head every now and then. She was just this bubbly, hilarious, enthusiastic story-spinner and knower of all things."

"Yep," says English-born McAlpine, "within two mouthfuls, all my motor skills went, and I was dribbling and slurring."

On the second date, they went to the beach. "Your boobs kept popping out of your top and I didn't know where to look," says Barton.

They were yet to kiss by the third date. Barton was being "uncharacteristically gentlemanlike" and McAlpine was getting nervous. She slid along a wooden seat to cosy up to him - and promptly embedded a large splinter in her bum. "It was the first time I saw her bottom," he laughs. "I tried to pull the splinter out but it was stuck fast."

After a trip to the emergency medical centre, she sat in the cinema with a numb backside and cried a flood of tears through Les Miserables.

She was crying over the film, not the discomfort. Since she was diagnosed with cancer in 2009, with a lump the size of a golf ball in her left breast, she's become an expert in managing pain.

It lingers in her body most days - a blinding ache in her side, or a stabbing so sharp and quick, she's stopped in her tracks. She's learned to dampen down the pain, telling herself "it won't last forever".

"I know it's going to get worse in the grand scheme of things. So right now an eight out of 10, I can push down to a three or four ... the eight is yet to come," she says.

"A lot of times I forget I have cancer. And then it hits me, pa-pow! And I think, how much longer is there left before it gets really bad? 'Til it's the end? There are definitely times when I get scared to close my eyes."

The morphine she took made her nauseous; the chemo exhausted her. But Barton was astonished by McAlpine's determination to keep packing her life with adventures.

"The first couple of weeks she was having chemo she was like 'C'mon, let's smash it in the bum, let's go and do something amazing'," he says.

For the past couple of years, the New Zealand Breast Cancer Foundation's poster woman has been rapidly ticking challenges off her bucket list, which is stuck to their fridge door. She's had a character part on Shortland Street, climbed back on a horse and piloted a plane again (she started flying in her early teens). She's worked at Weta Workshop, eaten a lot of pickled onions and landed - then sat on - a 65kg bronze whaler shark.

She saw a honey badger on her last trip home to England to visit her parents and produced a hit song, For Our Women, for the breast cancer campaign with a slew of Kiwi artists including Chris Knox, Tim Finn, Brooke Fraser and the Topp Twins.

Still to knock off the list: crash a car at high speed, blow up a building, break a world record, make her own fireworks, build a trebuchet (a giant medieval slingshot), and see Phil Collins in concert.

There's one she knows will be impossible to achieve: "Be completely clear of cancer."

But another she never expected - to fall in love again.

"I never thought in a hundred, million years I would ever find a relationship again, let alone one like this incredible love. He goes out of his way to look after me, to fill our lives with wholesome goodness that will make other people want to throw up in their mouths," she says.

And he says: "You're so eloquent."

Understandably, McAlpine is not always a bouncing spring. Towards the end of her last chemo treatment, around Easter, McAlpine would sleep all afternoon and well into the next day.

"I would bring her home, open up the french doors, and she'd lie on the couch while I pottered around and cooked," Barton says. "There's not a lot you can do other than be in the background, making sure she's okay."

The fact that McAlpine's health will deteriorate has been a delicate issue they struggle to broach.

"We dance around the edges," Barton says. "Helena has always told me she would never want me to look after her, to nurse her."

But he wants to, though "it's hard to envisage her being really sick. We need to talk about it in more detail, but that's difficult to sit down and do." An invitation for McAlpine to visit her local hospice has sat unanswered on the fridge for six months. She's just not ready.

There's no real indication how far away that day will be. In January last year she was told she had three months to live. And yet she's here, very much alive, a picture of blushing good health. But the cancer remains.

Barton's mother, who lives in Hamilton, had breast cancer 10 years ago, when he was working in London. She had a partial mastectomy and reconstruction, and radiation therapy.

"Mum was very lucky, in the sense that she is free of it now. She has a really supportive partner who found out everything to such a degree that I didn't try to understand the science of it," he says. "By the time I came back from London, Mum was on the road to recovery. I didn't really see her distress."

This time, he's had the support of close friends to help him through the troughs. "A couple of them I've poured my heart out to, and they've been wonderful. No one has ever told me to cut my losses and run," Barton says. "I would relish the opportunity to talk with someone out there who's been through this, though. The prospect of what could happen is the scariest thing."

He's taken heart from a new book released by the Breast Cancer Foundation, She's Got Breast Cancer - a collection of stories from Kiwi men who've also travelled the daunting journey alongside wives, partners and mothers. "The book is incredibly reassuring in a strange way; that you can manage it, you can handle it," says Barton.

McAlpine's friends are grateful, she says, that she has Barton in her life. "I don't think he comprehends how much my people absolutely adore him. How much they appreciate him making me so very happy, and a lot calmer as well," she says.

"I was always running around looking for the next big party, the next big excitement or distraction. We're not exactly homebodies now, but you get so much satisfaction from sharing your time with another person who fits on all levels. It's a wonderful, grounding relationship. It's just the easiest existence."

Barton has also had to fit in to the life of McAlpine's treasured daughter, Shannon. They are close, even though Shannon lives on Auckland's North Shore with McAlpine's former husband, Brett. He's been Dad to Shannon since she was just a few months old. Helena met New Zealander Brett in England where they worked together; they married and moved to New Zealand more than a decade ago.

"I never regret marrying that man. But there were 11 years between us; I was very young and got distracted after we got here," she says.

They have dinner with Brett and Shannon at least once a week. The two men have forged a friendship, and Brett has become a dependable sounding board.

"He's been a stunning chap from the very beginning," Barton says. "He's helped Shannon to get used to me, coached her through understanding what it means to her mum and me to have met each other. The four of us spend a lot of time together, it's nice. And Shannon's a really neat kid. It's hard when there's someone new in her mum's life. But she's been really good about me and Helena."

McAlpine admits she's been guilty of pushing people away in the past five years, particularly men. Every guy she dated, she asked the question: What's the point?

"I knew each time it wasn't a relationship I wanted to stay in anyway. Without wanting to sound corny or cheesy, this time it just happened, it clicked. An ease of conversation, a flutter of the heart."

She admits how biting it is that now she's had her ovaries removed, she's aching to have a baby.

"It got so intense after embarking on this relationship with Chris. It's been all-consuming. We are so happy, that potentially having that sort of future and knowing that I can't, is so frustrating," she says.

She also wants to yell from the rooftops to single women with breast cancer that there is hope of finding love.

"Of course, I got the last great bachelor in Auckland, like spearing the last humpback whale - I'm Captain Ahab with lumpy breasts," she says.

"A lot of women tend to think of their lives being over, regardless of what their situation is. But it doesn't have to be that way."

She knows how it feels to be self-conscious of a changed body: "I have one-and-a-half boobs, one nipple and huge scars. But he doesn't seem to see them as bad as I do. This is as close to paradise as you are going to get. I'm just so grateful Chris has made his decisions with me in them. I honestly believe this is a relationship that will go the distance."

And she hangs on to the line that Barton threw out to her: forever seems like a good place to start.

She's Got Breast Cancer is available free from the New Zealand Breast Cancer Foundation.