It has been a good year for British nonagenarians. Having celebrated their 90th birthdays in 2016, both David Attenborough and Queen Elizabeth were celebrated with big public bashes and lashings of biographical backpatting.

All richly deserved, of course. But now there’s a new kid on the nonagenarian block, and she has led the sort of jaw-dropping life that puts most of her contemporaries, royal or otherwise, into the halfpenny place.

“People tend to be either big fans or else they’ve never heard of her,” says John O’Rourke, a Dublin-born film-maker who has produced and directed a new documentary about the travel writer Jan Morris.

“She was a hugely public figure in the 1950s, and again in the 1970s, but has been a bit more retiring in recent years.”

O’Rourke’s film, which will be screened on BBC Two next Saturday, features Morris in conversation with the travel superstar Michael Palin – who, as he prepares to knock on the door of her house in rural Wales, confesses to being more than a little nervous about meeting a writer he has admired for many years and whose work has been a major influence on his own.

Within seconds they’re chatting over a pot of tea. Is she travelling much these days, Palin asks. “Oh, I’ve got tired of taking my shoes off at airports,” comes the 89-year-old’s brisk reply.

For O’Rourke the biggest challenge in telling Morris’s story was how to fit it all into a half-hour programme. During her career as a journalist at the Times and a teenage intelligence officer in the final years of the second World War Morris met Che Guevara, Kim Philby and Dwight D Eisenhower. She visited Hiroshima after the nuclear apocalypse. She reported on the trial of Adolf Eichmann in Jerusalem and climbed Everest with Edmund Hillary and Tenzing Norgay.

All these things, however, she did as a man – a man, into the bargain, who epitomised the machismo and derring-do of the brightest and the best of British manhood in the early years of the 20th century.

James became Jan James Humphrey Morris was born on October 2nd, 1926. At the age of nine he went to Christ Church, Oxford, as one of 16 choral scholars, all boys. He served in the 9th Queen’s Royal Lancers during the second World War. He embarked on a three-volume history of the British Empire. He

married Elizabeth Tuckniss and had five children, one of whom died in infancy.

Then, in 1972, James became Jan. It was a decision that, for most of us, could fairly be described as life changing, or perhaps earth shattering, but Morris insists that for her it represented not a change but a balancing, part of a lifelong continuum.

She and Elizabeth – who also features in the documentary – stayed together and, although they had to “divorce” thanks to the UK’s ban on same-sex marriage, recently marked their 60-year partnership with a civil union.

“The gender reassignment is a big chapter in Jan’s life story, but it’s not the whole life story,” O’Rourke says. Nevertheless he unearthed some archive footage that shows Morris’s dignified response to politicians and commentators who, following the publication of her memoir Conundrum, in 1974, accused her of having “disfigured” her body.

The pictures are fascinating because they show Morris in the act not simply of gender reassignment but of transition out of the mainstream. As O’Rourke points out, James Morris was far from being a rebel. “Jan’s upbringing was at the very heart of the British establishment, first at Oxford, then going into the Times, working in the Arab News Agency in Cairo, working as a spy in Palestine and Italy during the second World War,” he says. “And succeeding so tremendously in all of those.

“I mean, you have to be a very good musician to be a choirboy at Oxford, to be in the intelligence service in the British army, to be the one journalist at the Times to go up Mount Everest.”

The high point of O’Rourke’s film finds 26-year-old James merrily tackling the world’s highest peak in May 1953, dressed in short sleeves and a rakish hat, as if he were strolling up a Welsh valley. At 23,000ft he learned that Hillary and Norgay had reached the summit, which meant a hair-raising dash back down the mountain to file his copy.

“It was getting dark, and we had to go down through the icefall,” Morris tells Palin. “I was hopeless – kept getting tangled up in ropes and things.”

Although she makes it sound like a trip to the garden shed on a winter’s night it’s clear that Morris enjoys retelling the Everest story. Her lengthy, detailed reports in the Times were read by millions, and eventually enabled her to take a step away from journalism and start writing books, of which she would eventually publish more than 40 – including studies of cities, essays and several further volumes of biography.

Masterful observation Morris’s sophisticated writing style and masterful observation led the writer and critic Alistair Cooke

– no mean observer himself – to call her the Flaubert of the jet-set age.

If O’Rourke’s film – aided by a new biography of Morris by Derek Johns, to be published this week by Faber & Faber – sends people scurrying to reread Trieste and the Meaning of Nowhere, Among the Cities and The Great Port: A Passage Through New York, a new generation of readers have a lot of joy in store.

But seriously now. She’s turning 90, she’s had that mad life, she’s produced all those words. What did O’Rourke make of Morris, honestly?

“Very funny, very witty, great pleasure to be around,” he says. “There’s always a twinkle in her eye and always some mischief afoot. We were driving in convoy around the back roads of northwest Wales at a million miles an hour. Her house is beautiful, but it is really, really difficult to get to. And she’s very self-sufficient there.”

Does Morris reach any conclusions about life after almost a century of gobsmacking experiences? “Kindness. She says it’s the most important thing. More important than love, even, because you can be kind to everyone. You can’t love everyone.”

Artsnight: Michael Palin Meets Jan Morris is on BBC Two on Saturday, October 8th, at 9pm