Rushing to my local garage the other day to fix an urgent tyre issue, I was met by the rich, heavy scent of the mechanic who came to help.

Not petrol, diesel or oil, but, it turned out, the ambergris, jasmine and cedar scent he always wears. Maison Francis Kurkdjian, to be precise, which he buys from Selfridges at £480 a bottle.

We’ve met several times before, but I have no recollection of smelling this heady mix because, well, I literally did not smell it. I couldn’t.

It’s only in the past few months – having at last given up smoking after 50 years – that I have regained an acute sense of smell. And the world is suddenly a very different, at times rather overwhelming place, dense with scent at every turn.

It’s hard to know when the sense was lost, or at least severely limited, because like so many things in life, I didn’t ‘get’ what I didn’t have until it came back. All I knew was that others frequently commented on smells around them, but I’d never really understand what they meant.

Yes, I could smell a small amount. I suppose I suffered from what’s known as ‘hyposmia’, a reduced sense of smell. For example, I enjoyed the woodsmoke of Diptyque’s Feu de Bois candle as much as the next person (well maybe not quite as much) and hated the stench of the kitchen after cooking fish.

But now I realise that my decision not to install an extractor fan probably came from my diminished sense of smell since I was rarely bothered by cooking odours that penetrated the whole house.

Like everyone, I have a range of scents that are deeply nostalgic memory triggers and, fortunately, I have always been able to access them. The smell of a box hedge just after rainfall reminds me of the miniature box parterre we had in the front garden in Herefordshire when I was a teenager.

When Alexandra (pictured during her smoking years) entered her later 20s, her sense of smell began to fade

Alexandra Shulman says that only in the past few months has she regained an acute sense of smell, having at last given up smoking after 50 years

My mother would add lavender water to her baths and the smell returns her vividly to me. The green horse chestnut gelee of Badedas – my own teenage go-to with its tagline ‘things happen after a Badedas bath’ – brings back the anticipation of Saturday night.

It’s perhaps because of my previously limited sense of smell that, since my 20s, I have only used two scents – Chanel’s Cristalle, thankfully still available in its original crisp, grassy manifestation, and Miss Dior’s Eau de Toilette, Original (that Original is important, it’s become hard to get hold of and requires scouring foreign perfumeries to hoard supplies).

I have always been able to smell them, although now I suspect the reason why people would so often remark on the Miss Dior when I wore it – especially taxi drivers, curiously – might be because I would spritz on a huge amount.

What I have realised now that I can smell again is that I probably had as vivid a sense of smell as many people when I was young but as I entered my later 20s, it began to shrink. Not catastrophically but more of a slow fade.

For example, I have a very strong memory of my father’s skin – sweet, warm and distinctive – but no sense, from about my late 30s, of what other men’s skin smelled like, including that of my ex-husband and my current partner. I’ve read about falling in love with a person’s smell but I can’t say I’ve ever had that experience.

Much as I would love to say I would always recognise the smell of my son’s skin, I simply have no sense of it.

When he was a baby, he smelt delicious, as all babies do, but I attribute that to the Johnson’s baby powder and the tendency of mothers to think everything about their babies is delightful. During the Lynx years, even with my damaged olfactory sense, his bedroom certainly had a distinctive aroma that couldn’t be removed even with the skylights open. But over the years, now he’s left home, I’ve tried sniffing a favoured T-shirt or sweater left after a visit, hoping the lingering smell would bring him near me... and nada. Nothing at all.

We smell through olfactory nerves which travel from both the nose and the roof of the mouth (making taste a close connection to smell) on to the limbic system of the brain, which controls emotion, memory and mood. That’s why smells are so evocative.

Although humans are said to have fewer olfactory neurons (nerve cells) than many mammals, ours are acute, able to sniff out danger and have helped to keep us alive for millennia.

As many of us age, these neurons can become less effective but in my case the opposite appears to apply. Now 67, my ability to smell is as good as I can ever remember it being, if not better.

The fact is, the smoking habit that lasted more than 50 years had deadened it but not killed it.

It took a vast pulmonary embolism – generated by a seven-hour operation – to make me stop. The thought of puffing smoke anywhere near a life-threatening blood clot in my lungs held little appeal, and as soon as I was out of hospital, I chucked out my lighters, cigarettes, rolling tobacco and Rizlas. That was it. The end.

During all those years it never occurred to me that smoking was the reason for my blunted sense of smell, says Alexandra

Of course, going cold turkey like this was daunting. I stopped smoking during my pregnancy but, apart from that, had never been far from a ciggie since I was a teenager.

During all those years it never occurred to me that smoking was the reason for my blunted sense of smell, even though I knew both taste and smell could be affected.

Although I smoked regularly, I only smoked around five a day, and I simply assumed my poor ability to smell was something that was part of me, like having a terrible sense of humour.

It certainly meant I never smelt the cigarette smoke I puffed happily into every room in the house.

It was about six months after quitting that I realised that smells everywhere were getting stronger and stronger. At first, I didn’t compute what was going on and wandered around thinking how strange it was that there was such a powerful smell of the vinegar used to clean the house.

Running in the local park, I would often look at the spring bulbs – croci emerging from the mud after rains in January, the daffodils in March – but this year, for the first time, I have drowned in waves of scent wafting along the path, the resinous cistus, the exotic orange blossom.

Only last weekend on a coastal walk in Suffolk we clambered down a steep path bordered by yellow gorse and I smelt its thick vanilla aroma for the first time, though I’ve clambered down heaven knows how many gorse-covered paths in my life. Regaining this sense is a wonderful and unexpected bonus, adding an additional layer to everyday life. Everywhere I go there are new smells I am discovering, mostly pleasurable but not all to my taste. Some I find borderline disgusting.

Much to my horror, several of my expensive make-up and skincare items make me recoil. Having splashed out on the expensive Augustinus Bader face cream, I now can’t use it. Apparently, this £150 product is scent free, but not to me. I am assaulted by an underlying acrid, almost swampy, smell once it touches my skin. And a By Terry Brightening Foundation suddenly smells unbearable and has had to be binned.

While tangible, visible and audible are used to describe the abilities generated by touch, sight and hearing, there are no comparable terms for smell and taste.

Smell is hard to describe. It only exists by being compared to something else we recognise. But, having found smell after being deprived of it for so long, I now appreciate it is every bit as essential and life-enhancing as the other senses.