You don’t have to talk to Helen Davison for long to find that she feels strongly about things.

She’s friendly and cheerful but she’s got her passions. Urgency is noticeable in her voice when she talks about the need to tackle environmental damage before it’s too late, the need to defend the NHS, and the importance of public health and a fairer society..

In fact she reckons she felt too strongly to be a doctor. “Ultimately I worried too much,” she reflects.

So she eventually gave up medicine to become a full-time green activist - though she argues that the two are very closely linked. “Climate change is the biggest threat to public health,” she points out.

Helen was born 50 years ago in Cramlington in Northumberland and traces the origins of her green-mindedness to the weekend walks she was taken on as a child.

“We were brought up to appreciate birds and flowers. So I feel at home in the Lake District.

“When I was a junior doctor I used to escape all the craziness of the job by going walking in the countryside.

“When I’m on a mountain side I’m in my element.”

Her career in medicine didn’t have the same childhood origins. She was never one of those people who’d wanted to be a doctor since they were a babe in arms. Perhaps unusually, it was something of a default position for her.

She came from a family of doctors and was academically clever at school so she explains: “There was a certain expectation that I would do medicine or law. And I definitely didn’t want to do law.”

She studied at Newcastle University and came to Cumberland Infirmary afterwards. Yet Helen came to realise that it wasn’t for her. She had the knowledge and intelligence but not the temperament.

“It’s the greatest privilege you can have to help people with their health problems. But I would always go away worrying about patients.

“You shouldn’t do that, you’re supposed to think: ‘I’ve done the best I can,’ but I couldn’t. I probably cared too much.

“What you learn is that medicine is not black and white. I wanted it to be.”

Something else she’d acquired by this time was a hatred of waste. As part of her training she had spent time in a maternity hospital in Kashmir in India.

Needles there weren’t disposed of after one use, as they are here. They were sterilised and reused until they became blunt - and she found herself having to check their sharpness. “You wouldn’t have to think about that in the UK.”

Helen stresses that she’s not advocating the endless reuse of needles here. But she says: “What struck me in India was the waste that goes on in the UK. That’s just one example.

“There were kids playing in the street. All they’d have was a hoop and a ball but they were running around happy.

“Then you come back here and you see children being bombarded with ads for all this unnecessary stuff.

“It all sat uneasily with me. It encouraged me to buy more from charity shops rather than buying new.”

However she adds: “I never thought of myself as particularly ‘active’. My activism was within the doctors’ trade union, the British Medical Association.

“I was quite passionate about doctors’ well-being. I had got ill as a result of being a junior doctor. It’s all the hours, the stress, the pressure that doctors are under.

“When something’s wrong I feel a need to do what I can, in my way.”

Turning that instinct towards the environment came when she moved into public health - which had a deep influence on her.

“I became aware that the impact of climate change is the biggest threat globally to public health. There are floods and famines, people are displaced from their homes.

“As the temperature rises there’s an increase in the insects that carry disease. For instance we’re finding mosquitoes in places where we’d never seen them before.”

The World Health Organisation predicts that in 12 years’ time around a quarter of a million people will be dying every year as a result of climate change.

“Every time there’s a heatwave people die. Certainly in the European heatwave in 2003 there were more than 70,000 deaths attributed to that alone.”

And it’s not just in far-flung places. “All the things we should be doing for the environment are beneficial for our own health.

“If we insulate houses better we tackle fuel poverty. If we grow more of our own vegetables we eat more healthily.”

What also proved decisive for Helen was the Al Gore film An Inconvenient Truth .

“I was already aware that climate change was happening, but I couldn’t be sure whether it was just part of the natural cycle.

“This showed that it is down to human impact. We started burning fossil fuels and the temperatures started rising at the same time. It’s indisputable.”

She has no patience with the deniers.“The same people who were employed by tobacco companies to persuade people that cigarettes were safe are now being used to convince them that climate change doesn’t exist.

“When 97 per cent of climate scientists are saying something’s happening, that’s a very significant result.

“We are witnessing all the things that were predicted - glaciers melting, sea levels rising, coral reefs dying. Rain is heavier and lasts longer.

“You can’t blame one flood on climate change. But when we start getting regular floods, that’s down to climate change.”

Helen was one of the environmental campaigners from Carlisle who went to Copenhagen for the climate change summit in 2009 - the activists who later became Sustainable Carlisle.

“Copenhagen was a disappointment,” she recalls. “There were continuous talks, but the politicians just weren’t making the decisions that needed to be made to stop the carbon emissions.”

It’s going to take more than reusing our carrier bags and recycling our jam jars. “We need to influence politicians. It’s not just about individuals doing their bit.”

And she came to believe she could achieve more by campaigning on the environment than she could in medicine.

So Helen took the plunge - giving up the day job to devote herself full-time to green activism. Some savings and short-term work have kept her afloat.

She has no doubt it was the right thing to to.

“As a doctor I couldn’t always make the changes I wanted to be making. And I couldn’t give the energy needed for political activism.I wanted to make the biggest difference I can.”

Helen joined the Green Party and was their candidate in Carlisle at the 2015 general election. They stood aside in last year’s snap election, urging their supporters to vote Labour instead - and arguing for a “progressive alliance” among candidates who share some of the same values.

It didn’t happen elsewhere, and the Greens still have only have one MP at Westminster. Then there are still those who think they know better than 97 per cent of climate scientists and argue that climate change isn’t happening or isn’t down to us.

So does it never seem like a bit of an uphill struggle?

“Yes, it’s a challenge - but it’s really important that we are there to influence the other politicians and be a loud voice.

“To me a green, sustainable future is the only decent legacy we can leave our children and grandchildren - a place they can actually live in rather than somewhere we’ve trashed.”

Helen believes we are now “sitting on the edge of climate chaos” - so there must be times when it seems too late to avert it.

“I have moments when I think that,” she admits. “The tragedy is that we have all the knowledge and all the skills to make the changes.

“But you have to believe that activism can have an effect, as it did with votes for women.

“If we give up hope there’s nothing.”