FOR many Scots of a certain vintage, an iconic image from the early 1970s was the sight of actress Vivien Heilbron striding across a rural landscape in BBC Scotland's television adaptation of Lewis Grassic Gibbon's great novel, Sunset Song.

Its transmission was a defining moment. Not only was the novel considered "difficult" - as much for the uncompromising use of stylised Scots as for the uneasy sexual content - but here was a relatively modern piece of fiction hitting the screen at a time when Scottish literature was all too frequently ignored.

Adapted by experienced screenwriter Bill Craig, Sunset Song brought stardom to Heilbron in the central role of Chris Guthrie, who also acts as the narrator in the unfolding drama. To a certain extent it also made a star of the countryside in which it was set - the agricultural lands of the Howe of the Mearns, the wide vale of the north-east of Scotland bounded by the North Sea on one side and the foothills of the Grampians on the other.

Set in the farming community of Kinraddie in the days before and during the First World War, both novel and television drama make much of the fact that agricultural life in the Mearns is in its death throes and that what we are witnessing is the end of an old song. Certainly, Gibbon knew what he was talking about. A farmer's son, he was born James Leslie Mitchell at Auchterless in Aberdeenshire in 1901, and his family moved to the Howe of the Mearns when he was eight years old.

Sunset Song was published in 1932 as the first part of a trilogy entitled A Scots Quair. By any standards it is Gibbon's finest achievement, a novel of power, density and subtlety which created in Chris Guthrie one of fiction's great characters: a complicated farmer's daughter who becomes conscious of the land as the only continuing reality and the lonely permanence of a woman's place within it. Or as Gibbon writes early in the novel: "Two Chrisses there were that fought for her heart and tormented her. You hated the land and the coarse speak of the folk and learning was brave and fine one day; and the next you'd waken with the peewits crying across the hills, deep and deep, crying in the heart of you and the smell of the earth in your face, almost you'd cry for that, the beauty of it and the sweetness of the Scottish land and skies."

Small wonder that the novel became an instant sensation, and it is little surprise too that the 1971 television version cemented its position in the national psyche - so much so that a new generation accepted completely the concluding assertion made by the Rev Robert Colquhoun, soon to be Chris's second husband, as he unveiled the war memorial to the four men of Kinraddie who died in the conflict: "With them we may say there died a thing older than themselves, these were the Last of the Peasants, the last of the Old Scots folk."

The novel is currently being filmed for a second time, directed by Terence Davies (The Deep Blue Sea) and with a star-studded cast including Agyness Deyn playing Chris. With some scenes already captured in New Zealand and Luxembourg, shooting is now under way in Aberdeenshire using techniques the producers hope will "capture the beauty of the landscape", which they say will "feature as a character in its own right".

They also promise to remain true to the message of the original novel and to reassert Gibbon's literary values, and so they should. Even so, Davies and his company are straying into difficult territory. Not only is Sunset Song something of a national treasure, but since its publication the world has moved on.

When the book was first published, the First World War had ended only 14 years earlier and the aftershock of the conflict was still being felt. Even when it was being filmed for television, the First World War was still fresh in modern memory. People understood how the

countryside had been affected and how it was impossible to regard it as a land fit for heroes. In the decades after the war, farming in the Mearns was no longer able to offer employment to the army of horsemen, grieves, orra men and loons who once ran the big ferm-touns and won their work at the annual feeing markets. The heavy horse was gradually disappearing to be replaced by the tractor as farming began the long march towards agri-business and agri-technology. Although steam trains still puffed along sleepy country branch lines, everywhere the car was making the towns of the Mearns more accessible and the countryside less mysterious.

That much is made clear in the chapter Harvest, when the woods above Upperhill are cut down because the trees were "wanted for aeroplanes and such-like things". In vain does the factor promise that they will be replanted after the war, leaving local farmers like Chae Strachan to rage that it "would console him a bloody lot, sure, if he'd the chance of living 200 years and seeing the woods grow up as some shelter for beast and man; but he doubted he'd not last so long". In that sense, the war presages the wider changes that followed in its wake.

However, whenever dramatisation moves into the territory occupied by realism there is always the danger that it will sanitise the result; that what is intended as a eulogy for a lost way of life will be transmuted into sentimentality run riot. From the outset Gibbon had no intention of making Kinraddie and the Mearns sound like a rural idyll. In the novel, the new church minister says: "It was the Scots countryside itself, fathered between a kailyard and a bonny brier bush in the lee of a house with green shutters."

This is both clever and off-putting. The unofficial voice of Kinraddie which intrudes throughout the narrative complains that "what he meant by that you could guess at yourself if you'd a mind for puzzles and dirt, there wasn't a house with green shutters in the whole of Kinraddie". But for those in the know, the allusion is to the Kailyard school of literature which embraced rural sentimentality and pastoral morality. To it belonged Ian Maclaren's mawkish novel Beside The Bonny Brier Bush of 1894, while George Douglas Brown's novel The House With The Green Shutters, which appeared in 1901, borrowed many of the features of the Kailyard but put them in a more brutal and realistic setting.

So much, so entertaining as background literary information: the fact remains that Gibbon's Kinraddie is no Shangri-La, nor is it meant to be. The real world of the day was already passing into memory. Although Gibbon presented Kinraddie as a thriving, self-contained community in which men had employment and families lived in tenanted cottages, maintaining a thrifty domestic economy, there was another way of looking at it. The toil on the land was hard, the working day was long, there was no electricity and few cottages had running water or proper sanitation.

In 1917, a Royal Commission on housing in Scotland remarked that the average farm worker's house "has too often been selected not for its suitability as a site but for economy of land and the inconvenience of the farm worker. The result is that the site is often a contributing factor in the prevailing dampness of the houses, and aggravates the difficulties of water supply and drainage". The pay was poor, too, with men on the land being paid an average of £20 a year, and although the Agriculture (Scotland) Act of 1911 had extended the rights of security and tenure it was still easy for landowners to evict tenants from their cottages.

It would be convenient to sentimentalise that way of life and to make legends of the people who lived on the land, but as David Kerr Cameron has pointed out in his seminal work The Ballad And The Plough, an account of rural life in Angus and the Mearns, the area bred "dour folk; strange folk often droll to the point of eccentricity; folk with a humour so dry sometimes that it was just this side of maliciousness; folk whose pleasures were mainly simple and not infrequently carnal. They were people of a special strain, resilient and enduring; in another context their men became the backbone of regiments and their loyalty was heavily traded in the discreet corridors of Whitehall."

That latter comment has a resonance for the plot of Sunset Song and helps to explain the effect that the war has on the local community. Ewan Tavendale, who marries Chris, is brutalised after joining the army; he deserts and is shot by firing squad. The socialist farmer Chae Strachan is killed on the last day of the war. Long Rob of the Mill goes to prison as a conscientious objector but, having seen his world fall apart, then joins up - only to be killed in action. All are commemorated on Kinraddie's war memorial, along with James Leslie, about whom nothing is known other than that his name forms part of Gibbon's own real name.

The war brought about a sharp reduction in the numbers of people working on the land: in 1921, the census carried out by the Board of Agriculture showed that the number of male workers had fallen from 175,651 in 1911 to 169,984 10 years later. According to the board's findings, the decline was not restricted to any particular part of the country but was spread across Scotland. In the Borders, one investigator reported that "an old shepherd, who has passed all his days in the Cheviot country, stated that for every five persons employed on the land in his district, there was now only one". Soon machine-age farming would replace the draught beasts and with them went the cottars' tied houses as the face of farming changed forever, leaving Gibbon to remark that "the ancient, strange whirlimagig of the generations that enslaved the Scots peasantry for centuries is broken".

At the same time, life was often not any easier in the towns of the Mearns, such as Laurencekirk and Auchenblae, or in the more distant cities of Aberdeen and Dundee where conditions were not of the best. Due to a mixture of laissez faire attitudes, indifference to the plight of working people, ignorance of scientific advances and primitive approaches to sanitation, Scotland's main cities all contained areas which were contaminated by disease and crime and in which people lived lives of abject poverty in desperate surroundings. Visitors to Victorian Scotland marvelled at the country's growing wealth, but they were also appalled by the physical conditions and high mortality rates endured by the workers.

True, in the latter half of the 19th century, there had been some improvements in the provision of public health. Water supplies were modernised, sewage systems were brought into use and strides were made in combating epidemic diseases and introducing new standards in antisepsis, but the housing stock remained poor with crowded tenement buildings offering little in the way of elementary standards of hygiene. Water supplies were confined to single taps, there was little provision for even basic lavatories and these were usually communal privies, but overcrowding was the eternal and most serious problem. Most families lived together in a single room.

In that environment, men turned to alcohol for escape, thereby exacerbating the problem; women endured downtrodden lives trying to make ends meet and children were brought up believing that their lot in life was normal, perhaps even expected. Even at the beginning of the 20th century there was a hangover from the Victorian mindset which insisted that people living in slums had brought their misfortune on their own heads by acting irresponsibly and that they were incapable of prudence or forethought.

Conditions of that kind inform the plots of the other two novels in the trilogy - Cloud Howe and Grey Granite - which are set in larger towns on the edges of the rural area, but the impetus begins in Sunset Song. This is no rose-tinted novel but one set in an ambience where life is unyielding and hard and where people could be proud and robust but also mean-spirited and small-minded. Understand that and everything else in the novel - or film - falls into place.