Image: Robert Balog / Pixabay

PICTURE it: a relentless sun pierces a cloudless, azure-blue sky on a beautiful spring day in the far west of Cornwall. The coastal path from Mousehole to Lamorna, garlanded by burgeoning hedgerows and punctuated by the occasional croon of seagulls, points to a pub lunch at the Lamorna Wink, my reward for the morning’s peregrinations.

What could possibly mar this sylvan vignette?

Since you ask, I’ll tell you.

Nearing a clifftop promontory, the initially expansive path suddenly gave way to what I unfondly remember as a ledge.

Heart pounding, dry of mouth and jelly of leg, I froze with my back against the cliff, before me a vertical drop of… oooooh, 2,000, possibly 3,000 metres. Well, that’s my memory of it.

All I know is that I was stuck – unable to go forward in case what lay ahead was even worse than the stuff of nightmares behind.

Suddenly, from nowhere, a tweed-clad lady of a certain age in sensible brogues tipped her hat at me as she briskly passed in front, her excitable hound in tow.

“Morning,” she chirped, “lovely morning.”

Inching round the ledge, you’ll doubtless be relieved to learn I eventually made it to the Wink, a restorative G&T and the nice safe bus back to Mousehole.

And that, gentle reader, was the day I discovered that I’d joined the 20 per cent of the population who suffer from a morbid fear of heights (acrophobia). It went nicely with my fear of open water (thalassophobia), dogs (cynophobia) and that old faithful, flying (aerophobia).

As you can see, thanks to Kate (The Suspicions of Mr Whicher) Summerscale’s latest volume, The Book of Phobias and Manias, I can at least now put a name to my terrors. And I do mean terrors. Phobias, the north London-based author informs us, are diagnosed as fears that are excessive, unreasonable and have lasted for at least six months, they must also drive the sufferer to avoid the situation or interfere with normal functioning. Mere aversions are not phobias.

As its title might suggest, this highly readable book comprises an alphabetical canter through phobias and manias – which are in some ways opposites. “If a phobia is a compulsion to avoid something,” Summerscale writes, “a mania is usually a compulsion to do something.”

So from where do phobias (from Phobos, the Greek god of fear or panic) come?

Some, it is said, are the remnants of deep-seated primal survival instincts – falling from a great height would clearly do great harm, snakes and spiders could be poisonous – but that doesn’t account for an irrational fear of say clowns (coulrophobia), buttons (koumpounophobia), being without a phone (nomophobia), or popcorn (the imaginatively named popcorn phobia).

Fears triggered by past experiences make some phobias quite understandable – an attack by a cousin’s German Shepherd instilled my cynophobia, a hairy landing at Naples airport prompted my aerophobia – it’s when the fear becomes exaggerated or life-limiting that’s the problem. And why do canines and airplane terminals (!) trigger a fight or flight response in me when a nasty experience at the dentists has not left me with odontophobia?

As you can see, I’m now shamelessly using the phobias’ names, and Summerscale goes out of her way to explain them. Cynophobia, for example, is from the Greek for dog, kyon, acrophobia from the Greek acron, meaning peak. Then there are the fun ones. I particularly like the jokey aibohphobia, a supposed fear of palindromes, and hippopotomonstrosesquipedio-phobia, apparently a terror of long words.

So, now you’ve acknowledged and can even put a name to your phobias, what can be done about them? Do phobia-busting courses work? As in most things in life, yes and no.

A colleague cured her arachnophobia by handling a tarantula at London Zoo but my own experience was not quite the success I’d hoped for when I did a fear of flying course for a feature I was writing.

Sure, I was reassured when my instructor ran through aircraft safety… basic aerodynamics, engine reliability, wings and air pressure, that kind of thing. But he undid all the good work by introducing me to a whole new arena of terrors that had never crossed my mind. It had, for example, never occurred to me that the wings might fall off! And it didn’t help when he informed me he’d be reluctant to travel by helicopter because if the engine failed it would not flutter, sycamore seed-like, from the sky but plummet like a stone. Makes sense, I thought; it’s heavier than a potato.

We all know the risks of air travel are minuscule – there’s a one in 11 million chance of dying in a plane crash – but that doesn’t prevent an estimated 2.5 per cent of the population (including Summerscale herself) from suffering from aerophobia (I won’t bother to explain that one).

Frankly, I’m more drawn to a friend’s statistical gambit. He posited the idea of Irony Airways, an airline company that screened nothing but air disaster movies – Airport, Con Air, Snakes on a Plane, that sort of thing. He argued that the likelihood of your plane crashing while watching a movie about planes crashing was so remote it was practically impossible.

This is a handsome, fascinating, and yes, strangely comforting encyclopaedia of phobias and manias. Personally I found the former more interesting than the latter… but that may be because I have an irrational fear of manias.

I wonder what that’s called?

• The Book of Phobias and Manias: A History of the World in 99 Obsessions. By Kate Summerscale, published on October 6 by Profile/Wellcome Collection, £16.99