The stiff upper lip is as much a part of the British stereotype as our tendency to drink tea and talk about the weather. With the 87-year-old Lady Glenconner’s ‘keep calm and carry on’ attitude, her hit memoir is not such a bad book pick during a pandemic.

Her father was an earl – higher than a baron but lower than a duke. The Coke (pronounced Cook in a quirk typical of the British aristocracy) family have bowed and scraped to royalty for centuries.

Growing up near Sandringham, she was playmates with Princess Margaret, whom she would later serve as lady-in-waiting for thirty years. She recalls a childhood of stately homes, parents away on long voyages, WWII, wicked governesses, boarding school.

Things take a gaudier turn with her formal entrée to the marriage market, where she nabbed the very rich socialite Colin Tennant, 3rd Baron Glenconner, and was crowned ‘Debutante of the Year’ by society bible Tatler. Her father was a bit sniffy about the match – believing the Tennants to be miles below the Cokes.

Described by Princess Margaret as ‘a fairly decadent fellow’, Tennant was the life and soul. His party tricks included wearing paper underwear, then reaching down his trousers and ripping them off and eating them. Meanwhile, his tantrums earned him a lifetime ban from British Airways.

But Tennant – who died aged 83 in 2010 – is best remembered for buying and transforming the barren island of Mustique into a celebrity paradise. Photos show the couple at spectacular parties, surrounded by the biggest stars of the day.

Despite his rages and affairs, they made a good team, Glenconner writes, probably through gritted teeth. Yup, never a dull moment. Besides, one doesn’t dwell, even when one’s husband leaves his millions to a manservant.

Halfway through, we arrive at her three-decade stint as lady-in-waiting for Princess Margaret, whom Glenconner (understandably) wishes to defend from peasant biographers.

Being by Margaret’s side offered an escape from both her psycho husband, and tragedy; Glenconner has endured the deaths of two adult sons, while a third, Christopher, was left brain-damaged in a motorbike accident.

Princess Margaret was a supportive, compassionate friend, and most unfussy. She’d come to stay at the Tennant’s Scottish family estate with a kettle to brew her own tea in the morning. (She couldn’t actually operate a kettle, but it’s the thought that counts.)

The author always forgave Margaret’s ‘royal moments’. Behind the monarch, after all, she was at the very top of Britain’s rigid class system. And as for her rep for rudeness – her icy put-downs to commoners were usually well-deserved. Woe betide anyone who didn’t know their place.

Glenconner has worn many different hats – debutante, travelling saleswoman, maid of honour at the coronation of Elizabeth II – and been brought to life on Netflix’s The Crown. After a life well-lived by the Queen’s mantra: ‘Never complain, never explain’, her memoir is an interesting contribution to social and royal history. Her first crime novel – entitled Murder on Mustique – is out later this year.