Even to the able-bodied, climbing Britain’s three highest peaks might seem like a test of resolve. But Martha Lane Fox has had 47 operations, struggles with her balance, nerve damage and constant pain, and needs two sticks to walk anywhere – the legacy of a car crash 20 years ago that nearly killed her.

On Saturday she completed the first leg of “Martha’s Mountain Mission” by reaching the summit of Snowdon, or Yr Wyddfa. England’s highest peak, Scafell Pike, comes next, on 6 May, and she will be tackling Ben Nevis on 7 September.

“My body is not like other people’s,” she told the Observer. “I have massive pain and continence challenges, and I have very bad nerve damage. So all these things make it quite a significant hurdle to try and walk for a long time, let alone a really long time uphill, and all the way back down again.”

Martha’s Mountain Mission is a way for Lane Fox to mark the 20th anniversary of the car crash in Morocco. She was 31 and had just sold lastminute.com, the travel and gift company she founded with Brent Hoberman seven years earlier, and was on holiday with her boyfriend of six weeks, Chris Gorrell Barnes.

What looked like a new chapter in her life was nearly its ending when Lane Fox was thrown from the passenger seat of an open-top car and landed on a rock.

“I was very nearly dead,” she said, in a low voice. “They score you when you go into a trauma unit on a scale; I think it’s up to 39 – 39 is dead. I was at 37. So I don’t think I could have got much closer to death than I managed to get. And I was very, very broken.

“But I was extremely lucky that I had the capacity to firstly get out of Morocco – not that I organised any of this, my family organised it – and then be taken to one of the best hospitals in the country, the John Radcliffe [in Oxford], to be put back together, and then move to other hospitals over the next few years to be then continually put back together.

“So all of those things are not available to most people who go through something like that.”

That is one of the reasons she is walking – to raise £300,000 for four charities. Day One Trauma is for people in the situation that Lane Fox found herself in, helping people rebuild their lives after a catastrophic injury. There are myriad decisions to be made about medical treatment, finances and what they need to do to recover. “So if I have some grumpy moments, it’ll be the people at Day One Trauma that I shall be particularly thinking of [to motivate me],” she said.

Lane Fox broke 28 bones, had a stroke and spent just under two years in hospital, with surgeon after surgeon trying to fix, or simply alleviate, her injuries. For the last two decades she has been in and out of hospitals, an inspiration for another charity she supports, Horatio’s Garden.

“They build beautiful gardens and spaces by spinal units for people who are, like me, trapped in hospital for a very, very long period of time and can’t get outside,” she said. “It doesn’t really end when something like that happens to you. That’s life changed for ever. I’m lucky. I mean, genuinely, I’m not saying that in a glib way. I am lucky: I have resources and support to help me survive and thrive. So I do feel lucky.”

With support, Lane Fox has indeed managed to thrive, building on her dotcom boom success. Three years after the accident, she joined the board of Marks and Spencer, was appointed to the House of Lords and worked with David Cameron’s government to improve computer literacy.

Another of the charities is AbilityNet, which works with developers and technologists to remind them of the older and disabled people who are often excluded from digital life, and the fourth is I Am The Code, which wants to help a million girls and young women become coders by 2030.

Lane Fox became chancellor of the Open University in 2014 and in 2016 she had twin sons by surrogacy with Gorrell Barnes. The seven-year-olds, Milo and Felix, scampered along the path up and down Snowdon with her yesterday, along with more than 30 friends.

Still, the effects of her injury are ongoing. “I do a lot of physio anyway because otherwise I can’t exist,” she said. “But 2022 was a really bad year for me. I had sepsis and nearly lost my leg. I was really ill – I was back in hospital a lot of the time.” She turned 50 last year and had just one ambition: no time in hospital.

“It clarified my mind – I wanted to do something sufficiently terrifying that it would feel like a goal I had achieved but also sufficiently terrifying that people might give me some money to do it. So that was why I came up with this now somewhat nutty idea to climb the three peaks.”

After spending Saturday in the cold April sunshine in Wales, an exhausted Lane Fox was looking ahead to the next two challenges.

“It was much harder going down, but I’m alive and so elated by the day,” she said.

“Ben Nevis is the hardest. But one thing at a time.”

• To donate to Martha’s Mountain Challenge, visit givewheel.com