When Ben Goldsmith faced the loss of his daughter Iris, who died aged 15 in a quad bike accident in 2019, he discovered the healing power of nature – and became committed to ensuring everyone has access to it.

Goldsmith, a financier from a privileged dynasty of bankers and socialites, has become well known in recent years for his sometimes controversial proclamations on nature and rewilding, campaigning against intensive sheep farming, and for the reintroduction of wolves in the UK.

But it is only since his bereavement that the leading Conservative, who this month published a book about Iris and nature, has dedicated his life to the cause.

He explained: “In the aftermath of losing Iris, when everything seemed to be blackness and darkness, and I couldn’t really imagine finding any kind of meaning or hope or joy, or light or colour in anything, I found that my love of nature carried me in a way that I wasn’t expecting.

“There was a particular moment I remember so clearly. Just a few days after the accident, I wandered on my own, kind of bleary eyed down to swim in my pond. I just jumped into the pond and found myself feeling OK. It carried me, or held me in a way I hadn’t expected.”

After that, looking at his Somerset farm, he thought that he could bring back some of the nature to it, help it to heal and come back to life: “Doing that has given me more joy than any project or anything I’ve worked on all my life. The changes were almost instantaneous. As soon as we removed 50 sheep, 50 cows and removed 10 skiploads of barbed wire fencing, we rebuilt the stream, we filled in the ditches and ripped up the field drains and just let the land breathe. The place just felt like a kind of sleeping giant that was starting to awaken. It was like life was reawakening.

“I found spending time in that nature and watching this happen gave me a sense of joy and meaning and hope that perhaps was absent elsewhere because we were living with the terrible darkness of having lost Iris. And so for me being able to spend time in nature and even better having the privilege of being able to participate in the restoration of nature, was the most important thing in my life at that time, and remains so today because I feel that that’s the purpose of my life.”

For many of those who face a sudden loss, the feeling that it cannot be healed or fixed can be overwhelming.

“At the very beginning I found it impossible to cope with the feelings of wanting to fix something that couldn’t be fixed,” Goldsmith said.

He replayed the accident, in which Iris was trapped under an all-terrain vehicle on his Somerset estate, over in his mind, finding solutions that were impossible to enact: “I remember it felt like in a car garage when they take the car off the ground and raise it up. And then they rev the engine and the wheels don’t have any tarmac. So the engine over revs. Well, that’s sort of what my mind was doing. You know, as a father of young children, the person that is good at fixing problems and making things better. There was nothing I could do. So my brain just went round and round and round; what if she’d come a different day? What if she hadn’t driven that vehicle? What if the grass hadn’t been cut three days before and so she’d stuck on the track … there were so many what ifs. It drove me to distraction.”

But bringing life back to his land helped Goldsmith begin to recover. “Being able to heal something else and fix something else, perhaps in Iris’s honour too, perhaps that was the reason why it was so healing.”

However, Goldsmith realised that many people do not have the privilege of easy access to nature that he does. He says he has since convinced London’s Labour mayor, Sadiq Khan, to set up a rewilding taskforce to bring nature to underprivileged communities in the city.

“I think there is a terribly underappreciated and pernicious inequity in this country when it comes to access to nature. I think all human beings viscerally need contact with nature, even if they don’t fully know it themselves.

“I realised how unfair it is that people who live in the city often don’t have access to nature at all, particularly those that come from ethnic minorities and from lower-income backgrounds. There’s no reason why there shouldn’t be vibrant nature in the city; we should have wild, colourful, beautiful nature woven right through the fabric of our cities, people should have access to nature where they live, no matter where it is that they live.”

Although many Conservatives sympathise with landowners on the subject of public access to nature, Goldsmith has become sympathetic to the right to roam.

“I think there is an issue in terms of people’s ability to access the countryside in this country,” he said, “and that issue is no more pointedly illustrated than when you see beaches crammed with people like sardines, because the only place they can go is the beach. Now I find those pictures really depressing. The French and the Spanish fan out into their countryside in all directions when the weather’s nice, and they have access in all kinds of different ways. And so I think finding a way for people to access the countryside in a more fair and open way is really important.”

In this Goldsmith is at odds with many of his colleagues, who have railed against new nature-friendly farming payments and said eagles are not welcome in their constituencies.

“I disagree passionately and wholeheartedly with those elements of the Conservative party which are backward on the need to restore nature in our country,” he said with genuine annoyance, “and I take particular objection to the way that they use valid concerns around things such as food security, or the culture of rural society being under threat by nature recovery … and their arguments are completely without merit. I think they’re disingenuous and dishonest and wholly wrong. And I think they’ll be left on the wrong side of history as these things advance.”

Goldsmith says he has not ruled out backing Labour in the next general election, if the party puts out a stronger proposition than the Conservatives for nature.

“I will vote for the candidate that is the most ambitious on nature and climate in my constituency,” he said. “It’s by far the biggest issue, and I would absolutely spend my money on and give my vote to anything that’s going to advance that agenda.”

Goldsmith, whose brother Zac is a Tory peer and minister, was on the board of the Department for Environment, Food and Rural Affairs until last year. He found it an eye-opening experience.

“When I joined the Defra board, I was horrified to discover the degree to which the National Farmers’ Union and also the industrial fishing representatives were able to influence government policy. There was an old boys’ club and a bit of a revolving door approach, whereby they all knew each other and anyone who dared stand up to those two industry representative groups was cowed into submission very quickly.”

He added: “We are winning. A lot of the rage we see in the papers and on social media today from those interests is coming about because they know that their influence is starting to wane, and that their grip is loosening and that the British public, and journalists and politicians are waking up to how absolutely trashed nature is and how things really do have to change.”

God Is An Octopus by Ben Goldsmith (Bloomsbury Publishing PLC, £20). To support The Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.