I was at the Borders Book Festival 2018 tonight, to see Prue Leith being interviewed. More on Prue in just a moment, but I must first give this amazing festival a plug. It’s held in Harmony Garden, overlooking Melrose Abbey, and boasts a four-day line-up of phenomenal speakers, alongside a plethora of food stalls selling everything from artisan pizza to home-made crème brûlée. We found the Festival vibrant, welcoming and entertaining and I’d return at the drop of a hat.

Throughout her interview, Prue regaled us with amusing anecdotes, including one in which Prue proudly presented the Queen with a cup of tea only to find out that she had made said tea in a way that the Queen particularly dislikes (“The damehood’s still waiting”, she cracked).

Prue Leith may be 78 years old but she is living proof that age does not need to slow you down and is definitely no barrier to success. Having recently remarried, Prue is now at the helm of the perennially popular ‘Great British Bake-Off’ and has re-published her memoir, ‘Relish’. She has also just written a new cook book – and describes herself as “embarrassed but grateful” for the deluge of ‘Bake-Off’-related publicity benefiting its promotion.

I hadn’t known this, but Prue actually gave up writing about food for 25 years to concentrate on being a novelist. Eventually, she was tempted back into the world of food by ‘Great British Menu’, in which she participated for eleven years. From where, though, did this inspirational septuagenarian’s love of food stem – and how did she break into what was once very much a man’s world?

Growing up, Prue told us, she knew nothing about cookery; as a “white, privileged young woman” in South Africa she had no need for domestic skills. Having eschewed university and “floundered” for a while, Prue moved to Paris, where she became fascinated by food “like everyone else in France”. Next stop: Le Cordon Bleu in London, where Prue learned classic French cookery – skills she put to good use catering for dinner parties. This says Prue, was a whole new world: one in which rich Belgravia housewives bought the ingredients she needed on account at Harrods and passed off her cooking as their own.

It was at one of these dinner parties that Prue met a City of London butler who recommended her services to a firm of stockbrokers. This was the break into the world of business that she needed, with some lucrative contracts coming her way.

And then: a life-changing slice of success: Prue won a high-profile catering contract with the Orient Express. This propelled her into the big time; contracts with the Queen Elizabeth II Conference Centre, British Rail, the Edinburgh International Conference Centre and Hampton Court Palace followed.

Those successes enabled Prue to fulfil a life-long ambition and open her own restaurant: Leith’s, in Notting Hill, which she owned for 30 years. Asked for the secret to its success, Prue responded: “It’s simple: the customer is always right”. It pays to make friends with your customers, she advised – and to say sorry when things go wrong.

Good reviews help, too – Leith’s became a celebrity hot spot after Humphrey Lyteltton gave the restaurant a glowing write-up in Tatler, with The Beatles (who loved a fry-up), Lulu and The Hollies all becoming regulars.

Approaching 50, however, Prue found her circumstances changing. Her husband, who was 20 years older than her, was unwell, her business, which by now employed over 500 people, was all-consuming – and Prue had aspirations as a novelist. Taking a leap into the unknown was a gamble, she admits – but one that paid off, as she has gone on to publish seven novels.

Perhaps inevitably, Prue found herself unable to stay away from the world of food for good. In 2016, ‘Great British Menu’ came calling and Prue found herself back on our TV screens in BBC2’s highly successful competition for top chefs.

You would think that, when Prue left the show in 2016, she might have been thinking of slowing down – but no, not a bit of it. Instead, she turned her eyes towards the biggest prize of all: ‘The Great British Bake-Off’. Refreshingly, Prue admits to very much wanting Marry Berry’s job when she found out Mary was leaving the show, “ but I didn’t think they would want another old lady”. Channel 4 had other ideas, however, invited Prue to audition with Paul Hollywood.

“I was very nervous”, she confesses, “and didn’t want to tread on anyone’s toes – but Paul told me to forget my nerves and push him out of the way!” Sound advice – which obviously worked.

What next, then, for one of the nation’s best-loved female icons? The new cookbook, ‘Prue’, comes out in October. “I called it that because I want to be known by my first name like Delia, Jamie or Nigella!” What she really wants to do, however, is write a book about left-overs “and I’d call it ‘Left-Overs and Fuck-Ups’, although I’m not sure that would get past my publisher!”

It would take a brave woman or man to say no to this immensely-likeable force of nature. Risqué book titles aside, I suspect that there is still much, much more to come from Prue Leith.