Ruby Wax and Mel B on on Trailblazers: A Rocky Mountain Road Trip

Airing on BBC Two, the three-part docuseries sees the trio embark on an epic adventure as they re-trace the footsteps of intrepid Victorian explorer Isabella Bird, whose exploits have largely been lost to history.

"Isabella is my heroine," declares 69-year-old Wax. "We were (on a journey) seeing what a woman could do more than 100 years ago, wearing nothing, sleeping in the snow and being so brave...

"To me, she's the beginning of the whole feminist thing, and yet we never hear about her," the American comedian quips with passion. "I was thrilled to do it with Emily and Mel; I knew that we were going to click, but it was really important to follow the trail of this woman, otherwise, what's it about?"

At a time when most explorers were men, Yorkshire-born Bird was certainly a trailblazer. Being prescribed 'mountain air' to cure her malaise, in 1873 she set off on her travels across the globe to find exactly that.

Travelling alone in what was a restrictive era for women, she crossed the lawless American Wild West during the Gold Rush era, riding a staggering 800 miles on horseback through the Rocky Mountains of Colorado. She befriended outlaws, climbed mountains and even faced grizzly bears.

"These are like the unsung, forgotten heroes," muses Brown, 47. "And I've never heard of her. It's not in our history books. Why are all these women not being praised and celebrated?"

They soon will. And who better to emulate this iconic journey than three modern-day trailblazing women forging their way in their respective careers?

Using her original 1873 book, A Lady's Life in the Rocky Mountains, as inspiration, the threesome set out to explore the people, places, and curious customs of an ever-changing America, while also reflecting on the changes in Western society over the last 150 years - and bonding over their own experience of womanhood.

For 32-year-old Atack, who had not heard of Bird and her exploits, it was the latter that initially drew her in.

"It was presented to me as, 'You're going away with two legends, Ruby Wax and Mel B, the Spice Girl'. And I was like, 'Well, obviously, I'm going'. I'll go anywhere in the world with those two women because I've idolised them my whole life.

"But then learning more about what we were going to do, I was thrilled, because I really come into my own when I'm physically and mentally challenged..." says the former Inbetweeners star. "I'm always very open with how, at times, I struggle with my mental health. And the way I overcome those things is by getting out there in the world and challenging myself."

From horseback riding and mountain climbing to learning to lasso and communicating with wolves, it's an unforgettable voyage in pursuit of a forgotten pioneer.

But is there a particular standout moment?

"Each thing we did, I thought, 'Surely it can't get more dangerous' and each time it became harder," Atack recalls. "We started with the horses in the mountains and then we had to practice mountain climbing before we climbed Pikes Peak at the end.

"All of it was overwhelming - but it does me good to take myself out of my comfort zone."

"What I found interesting was when we went to Aspen (and learned about the Gold Rush) ..." shares Wax. "These miners came and they gouged out the size of the Grand Canyon into mountains and destroyed America, raised it to the ground, because they were so greedy.

"I could see the story of why America became what it became, which is decadent and ruthless. And they don't know when enough is enough."

Though "this was a road trip of a lifetime," chimes Brown. "It was almost like you were doing a bucket list check off because the places that we went to, the people that we met, the scenery, was incredible.

"We were three girls from three different walks of life, coming together, helping each other figure stuff out, having an absolute blast doing it and making good TV that is actually informational."

As for what she learned, "that I'm actually the sane one amongst those two..." quips the Spice Girl, laughing, "And how open I am for challenges and really (enjoy) putting myself out of my own head and into somebody else's shoes.

"But it made me think how much I really do love my own company - and I think Isabella must have loved her own company to be able to do what she did, with no steady companion by her side."

"I envy people that can be on their own," Atack offers.

"I always say, I hate being alone. But actually, what I discovered doing this, even though we were doing things together, it's very much an independent mindset that you have to be in when you're physically trying to grip onto a mountain.

"Though I feel like I surprise myself every time I do something like this, like when I did the (I'm A Celeb) jungle," she compares. "I've been led to believe that I can be physically quite useless. I've been labelled a bit of an airhead, really, for a lot of my life, but it's just not the case."

Wax, meanwhile, talks of her happiness at living a simpler existence, admitting: "I'm very envious, not of Aspen, but of that side of America where it's so beautiful, that if every day you just get up and get an eyeful of that..." she trails off. "I would rather live like that, to be honest."

"We used to have in-depth conversations with each other," Brown remembers fondly. "And one thing I found about you, Ruby, is that you're similar to me in a way where you can just go off to a silent retreat, not talk for 30 days, and immerse yourself in that peace and quiet and go inwards.

"That's one of the reasons why I moved to Leeds, because literally I go on a six-mile walk and its complete forest round here, and I don't see a soul. It's so beautiful just to be surrounded by nature and beauty. So come on down and stay with me, Ruby and Emily!"

"I would love to be able to feel secure enough to be at peace like that by myself and do those things," responds Atack. "I try hard but it's a work in progress."

Though despite different traits, "I think there's a rooted similarity with all three of us, in the fact that we are trailblazing women, we're rule breakers," she considers. "We've done things in our own way, in our own path in, in a world where it's harder to do that as a woman."

"But I couldn't have done this trip in this way without Ruby and Mel. It would have been a completely different experience," she finishes. "I needed them on that trip. It was a Godsend that it was them."

Trailblazers: A Rocky Mountain Road Trip starts on BBC Two tomorrow (Monday, November 28)