In 2016, that most eventful of years, Isabel Hardman went from being a successful and widely-liked journalist — an unusual quality in political writing, where many of its practitioners on both the left and right revel in the abuse that they receive — to, in her words, “a gibbering wreck”. Unable to string a sentence together, the Spectator assistant editor ended up leaving the Conservative party conference in Birmingham that year under heavy sedation, with “obsessive, frightening thoughts settling like a parliament of rooks, noisily distracting me from anything and everything”.

This was a sharp decline from her previous success of being named Journalist of the Year at the 2015 Political Studies’ Association annual awards. Hardman was so indefatigable that she filed revelatory stories “from children’s birthday parties, crammed Tube carriages, pub toilets and, of course, my bed”. The loss of her ability to formulate sentences was a dreadful blow for this most articulate of writers: “Words were how I made a living: thousands of them every day on what British politicians were up to now. I was garrulous: long car journeys across the country could be taken up with all the words I had to offer, on any subject, pausing only when friends managed to interject.”

She leaves it deliberately unclear as to why this spectacular crack-up occurred at the start of 2016, writing briskly that “I don’t want to tell the full story, nor do I think it would help the reader particularly to know it.” She describes it as “a serious trauma in my past”, and indicates that she is not sure she will ever want to write about it.

Still, perhaps inadvertently, she offers tantalising details: “It was bad enough to make the jaws of healthcare professionals sag a little in shock whenever I told them. It made one of my burliest friends cry when I told him. I still notice the fists of family members clench with horror whenever the subject comes up.” One can imagine that a publisher might have pressed her even to include these brief insights. Her reticence is all the more striking because of how candid she is otherwise.

Hardman’s account of her partial recovery from her breakdown, is a considerably more interesting and accomplished book than a simple wallow in the details of her ordeal. The title is easily misread. Rather than either a social history of the NHS or an autobiographical account of what befell her, Hardman instead examines the healing powers of nature and the great outdoors, arguing that their therapeutic powers can contribute immeasurably both to our mental and physical health. It is deeply unfortunate timing that the book is being published at a moment when her readers are largely confined to their homes for their own health and safety, but the central message will outlast any pandemic.

Hardman is a precise, lucid writer, never afraid to offer well-argued opinion but always careful to delineate it from factual reporting. She writes, “It is only recently that society, and even the medical establishment, has started to acknowledge that our physical health and our mental health aren’t as separate as we assumed.” To those who grew up knowing the maxim “mens sana in corpore sano” — “a healthy mind in a healthy body” — this may not be the revelation that Hardman presents it as, but at a time when enlightened GPs prescribe birdwatching and long walks alongside pills and psychological treatment, a greater belief in the natural, as well as national, health service will ultimately do Britain a substantial amount of good.

Hardman comes across as a thoughtful and intelligent head girl or JCR president, forever exhorting others

The sainted NHS itself does not emerge from Hardman’s book with particular credit, especially when it comes to mental health care, which she regards as underfunded and loaded with stigma. One professor describes a phenomenon known as “diagnosis creep”, which can lead to otherwise healthy patients being medicated because they feel justifiable anxiety or depression about a circumstance such as a bereavement, or indeed a national disaster that confines them to their homes for months.

As the NHS’s national mental health director puts it, “drugs and therapy alone cannot bring about healing”, although one has to hope that we never end up in the absurd situation that some other societies have arrived at, where an ever-growing number of “assistance animals” are said to be invaluable to their owners’ mental health, although Hardman makes a convincing case for therapy dogs.

The unwell can be helped in less zoological ways. Hardman was a keen gardener even as a child (“I was unusual in knowing the common and Latin names of most garden plants by sight”) and views it as a straightforward way of keeping oneself occupied and happy. She runs long distances and swims in freezing seas and rivers, relishing the necessary endorphin release of the “runner’s high”. In the case of swimming, “the most powerful antidepressant I have ever encountered”, she plunges into water in the depths of winter even as she tacitly acknowledges that there is a masochistic element to how far she pushes herself. Better to cause some physical damage, which will swiftly heal, than endure mental distress, which could last indefinitely.

Natural Health Service is rich in interesting and unusual details. Birdwatching is considered a useful way of distracting oneself; twitching, a more specialised pursuit requiring a near-obsessive interest in the travels of particular birds, is not.

Hardman balances her universal and personal writing with skill. She writes of her relationship with the former Labour MP John Woodcock, a self-confessed “grumpy bugger” who himself suffers from depression: “When we started our relationship, a diary piece appeared in one of the newspapers pointing out that both of us had written about our mental health problems: a rather less glamorous set of things in common than most couples would aspire to.” These glints of dark humour are a welcome tonal shift in what is generally an earnest and thoughtful book.

Hardman comes across as a good-natured, thoughtful and fiercely intelligent head girl or JCR president type, forever exhorting others and being exhorted herself in turn. It comes as little surprise to learn that she has never so much as smoked a cigarette, let alone taken any harder recreational drugs. Her biographical disclosures have an unsentimental hardness to them that removes any hint of twee.

She admits, bluntly, that the outdoors alone can’t cure sufferers and is still unwell herself, taking large doses of the antidepressant drug sertraline. She openly refers to herself as having “mad” spells, as a useful way of distinguishing episodes of ill-health from everyday depression, even as she acknowledges that referring to others by this title might well sound pejorative.

She concludes with a sensible, thoughtful “manifesto” of how the Natural Health Service might work for people, taking it from a luxury to an everyday essential, but the compassionate message readers suffering from their own mental issues should take away is a simple one: hold on.