IF you had just one word to describe Neal Ascherson, it would have to be twinkly. It’s most obvious in the eyes, but it’s everywhere else in his mien too: in the half-smile on the lips, the good-natured cast of the face, in the genial demeanour and, of course, in the sparkling conversation. I’m treated to an hour and a half of it today. Other people – the friends, colleagues and contacts he has cajoled and charmed during his long career in journalism – have enjoyed it for years, even decades.

Then again it seems facile to limit yourself to one word to describe Ascherson when his is a career characterised by a constant flow of words, millions of them, published in the many newspapers he has worked for and in the dozen or so works of history and biography he has written; served up through his long association with the London Review of Books and its New York equivalent; spoken in lectures or on the stump (he stood unsuccessfully for the Scottish Parliament in 1999); or penned for others to read aloud in TV programmes such as seminal documentary series The World At War.

Until this year, however, there was nothing in all those millions of words that wasn’t entirely grounded in fact. But now, aged 84, Ascherson has published his first novel, The Death Of The Fronsac.

“These anecdotes and stories have been churning around in me for all these years and I felt I must get them down,” he says simply, when we meet in the Edinburgh flat of a friend of his and I ask: why now? “I’ve made various attempts in the past which weren’t any good at all and about four years ago I thought if I don’t do it now I’ll never do it.” In fact, he adds: “In many ways this book is just an assemblage of stories I stole. Some of them happened to me, some are versions of stories I heard from other people – many, many other people. And like all journalists, from even before I was a journalist, I just accumulated stories.”

Written from the viewpoint of an old man looking back on his life, the novel is set against the background of the Second World War and tells the story of Jackie, a young girl living in Greenock, her mother, and a Polish officer billeted with them and attached to the French navy. The novel begins with the sinking of a ship in the Firth of Clyde – an event based on the accidental destruction of French destroyer Maille Breze in April 1940 – and widens to encompass a story of betrayals, damaged lives, recriminations, secrets large and small and the experiences of the Poles during and after the Second World War.

Poland and its people have long held a fascination for Ascherson. It started at school when he picked up a Ministry of Information leaflet on Polish history, published to give context to the presence of Polish forces in Allied ranks and on British streets. “I was completely blown away,” he recalls. “All their dates are different, all the things that were great for us were terrible for them and vice versa.” It was his first realisation that the history he was being taught at school, what he calls “British-point-of-view history”, was simply one way of looking at a hugely complex set of competing stories. That realisation has coloured much of his writing since and much of his understanding about world events.

To date, he has written three books about Poland’s search for identity and its various political struggles, and even today he characterises himself as a keen Poland-watcher. The present government, dominated by the right-wing populist Prawo i Sprawiedliwosc (Law And Justice Party), he describes as “frightful” and marking a return to the “ultra-patriotic, ultra-nationalist, ultra-paranoid” mindset which has gripped Poland regularly through the years. “But what a country of stories,” he adds. “It’s just amazing.”

Ascherson first visited in 1957. It was a year after the country had thrown off direct rule from Moscow and in place of that had come “a sort of socialist democracy which everybody on the left in the West thought was great – Marxism and yet democracy at the same time. Of course it didn’t last. But for the Poles it was delirium, having been cut off from the West since 1939. Suddenly, at last, people were coming in and the outside world was tangible”.

He was working for the Manchester Guardian at the time but as they refused to fund the trip he travelled independently, armed with 300 Canadian dollars he’d picked up somewhere and which he converted into an “outrageous amount” of zloty. He checked into the best hotel he could find and “lived like a king for three unforgettable weeks. Everybody wanted to meet me and talk to me and buy me vodka. All the beautiful girls wanted to know me. It was just extraordinary. But I really got to love Poland and Polish people for their courage and their extraordinary, gallant kind of style”.

More than all this, however, The Death Of The Fronsac also reveals a writer reflecting on his own life through the medium of fiction.

“It is in a way autobiographical,” he concedes. “But it may be more autobiographical than I realised because since I finished it a number of people who have read it have said, ‘Ah but this is about you! It’s all personal’. Often I didn’t really realise that.”

The easy part of the autobiographical content to pin down concerns the time Ascherson spent in Greenock as a child. Born in Edinburgh in 1932, the son of a naval officer, he was the same age as Jackie – nine – when he arrived in the town a year after the sinking of the Maille Breze. The family lived in Union Street for three years and later moved to nearby Kilmacolm.

“I saw things in and around Glasgow and the west of Scotland in the 1940s that now I can’t believe,” he recalls. “I remember seeing in the Broomielaw a huge great horse-drawn wagon stacked with sacks of sugar. And then suddenly, out of nowhere, came these wee boys. It was winter but they were barefoot and scabby and ragged, and they had knives. And they leapt on to the back of the wagon and slashed the sacks and they were eating the sugar with their hands. Now that’s the kind of image you never forget.”

Ascherson’s own childhood was very different, however. Though his father veered to the left politically (he was an avid reader of The New Statesman), his son was sent to a prep school in Dorset. “A ridiculous idea,” Ascherson laughs. “I don’t know why my mother thought I was safer in the war in the south of England than on Clydeside. In fact it turned out to be one of the Germans' main invasion targets … they were going to land a parachute brigade about a mile away from where my school was.” The intention then was for him to go to the Edinburgh Academy, one of Scotland’s top private schools, though as it turned out Ascherson went up several divisions even from that: to Eton, where he won a place as a scholar.

He would later study at King’s College, Cambridge and emerge with a first in history. But prior to university he spent a year as an officer in the Royal Marines during the so-called Malayan Emergency, which pitted the British against the Communist-backed Malayan National Liberation Army (MNLA), a guerilla insurgency. Ascherson’s experiences in Malaya haven’t been directed into fiction (yet), but just as his early childhood is now a cause for serious reflection, so is one particular event from the year he spent in the jungles of south-east Asia.

It came after an encounter with a group of guerillas. Two were mortally wounded and Ascherson shot them both. He was 19 at the time. “For many years, I remembered it of course,” he says. “But it didn’t trouble me. I just thought, ‘What else was I supposed to do?’ I did it. So I didn’t agonise about it.”

A decade ago, however, he started to think differently. “When you get old you do get more fascinated by life itself, the fact that people are alive as opposed to not being alive, and the extraordinary privilege of being alive, as I still am. So about 10 years ago or more, that began to come back to me in a different way, and I thought however you excuse it or legitimise it, I took their lives and they were young. OK they were dying, they wouldn’t have lived anyway, yes that’s all true. But it was I who brought their lives to an end. And you think, ‘Well, I’m sorry for it’, and all the justifications don’t take away from the fact that I did it.”

Neal Ascherson’s voice has never been muffled and it has certainly never been ignored. But for the last half-decade or so, his words have been more keenly sought than usual, and as a result his voice has carried far. The reason? The 2014 referendum and Ascherson’s clear-eyed and always cogently argued support for Scottish independence.

His belief in it dates back to his teens, when he signed the Scottish Covenant organised by Home Rule advocate John MacCormick. He added his name when it landed on the wet slab of the fishmonger’s in Kilmacolm. Two million other Scots did the same. He even took a copy of it with him when he went to Malaya. The expats he met there, many running rubber plantations in this last corner of Empire, mostly just laughed.

Twenty-five years later, marking the slow approach of the 1979 devolution referendum from the political desk of The Scotsman, he watched momentum gather behind another bid for self-determination. It may not be much of a sop to those who felt their world had collapsed when they woke on the morning of September 19, 2014, but for Ascherson the fallout from the 1979 result was much worse. When I ask him about low points in his life, he mentions his first marriage – to Corinna Adam, also a journalist – but also that 1979 vote.

“I felt deeply depressed … I think it lasted quite a few years,” he says. “And I was very aware of what it had done to people around me, my friends, and how shattered they were by that. Really, really shattered. Some of them just gave up and went away. Some went south, some went to America and places. Some went on the bottle. Others went to drugs. It was just awful. Terrible. Overnight Scottish politics practically ceased to exist.”

Ascherson’s marriage to Corinna Adams ended in 1982 and in 1984 he married the Aberdeen-born journalist and broadcaster Isobel Hilton. They live in Islington in London and have a son and a daughter. I ask Ascherson what relationship they have with Scotland, Scottishness and the idea of Scottish independence.

“They grew up in London, they’re Londoners,” he replies. “I think they think of themselves as British. They have a kind of hopeful identification with Scotland, which of course they know. They come to Scotland a lot. And they’re deeply in favour of independence.”

He adds:”If Scotland were independent and the SNP were still in charge then there would be an offer of citizenship for which they would qualify. And I think they’d both take it up.”

Today, he’s still broadly optimistic about the prospects for Scottish independence, though he admits the movement is going into “a slump”. “It’s sliding down into a period of indecision and discouragement and a certain amount of internal back-biting, but I don’t think that’s as serious as people make out. But obviously it will eventually re-emerge. No independence movement in history which has attained the kind of scale that was attained in 2014 dies out.”

What about Quebec? “Quebec will come back,” he says, without a pause. “It’s very interesting. The Canadians are always saying ‘Oh that’s the end of Quebec’, but it always comes back.”

And just as Quebec is instructive, so there are lessons to be learned from the Polish experience. “I think one lesson is that Scotland is very fortunate not to have to hang its independence project on language, for instance, or ethnicity, and simply to say, ‘This is a matter of democracy and justice and this is what people may come to want in a majority and it should be done’,” he says. “And above all to be careful about victimology – that Scottish identity depends on being aware of the awful things that were done to Scotland by other people. A lot of bad things happened to the world that were done by Scots.”

Ascherson holds fast to the notion, celebrated by some and derided by others, that Scotland is a mongrel nation, finding in it another difference between Scottish nationalism and other, more virulent sorts. “There’s no pretence about ethnic nationalism in Scotland,” he says. “There are a few bampots who go down that blood and soil route, but basically it’s political. It’s about politics and democracy – and identity to an extent – and about justice.”

In terms of the future, he identifies “two large, swithering constituencies” which must be won over. One contains those people who don’t really want independence but see it as inevitable, the other holds those who do want it but just don’t think this is the right time, for reasons of economics or wider, global politics. When the swithering stops and those centrist constituencies align behind the independence project, it will become unstoppable.

“I think independence will certainly happen,” he says.

Ah, but when? “Well probably not in my lifetime. I’m getting so old.”

The genial half-smile plays on, though, and don’t think for a moment the twinkle is dimming yet. Those words will continue to come.

The Death Of The Fronsac by Neal Ascherson is out now (Apollo, £18.99)