The old woman who introduces herself as Helene Schjerfbeck is not who she says she is. As she hobbles through the Finnish coastal town of Tammisaari, dressed in the kind of heavy black cotton dress that went out of fashion some time in the 19th century, she points out some noteworthy spots: here, a tree immortalised in a picture that hangs in the national art collection in Helsinki; there, the old piano teacher's house which once provided lodgings for Schjerfbeck, now regarded by many Finns, 73 years after her death, as their country's greatest artist – and the subject of a major new exhibition at the Royal Academy in London. Shielding her eyes from the glittering Nordic light and gesturing towards the upstairs window of a pastel-pink cottage, the ersatz Schjerfbeck says: "I lived there once" (although, in truth, it's unlikely this woman has ever been inside that building). "It was a lovely time."
It was 1918 when the real Schjerfbeck first set foot in Tammisaari, a Swedish-speaking community also known as Ekenäs. She was enjoying a break from the one-bedroom apartment in Hyvinkää, 70 miles away, that for 15 years she had shared with her elderly mother, "torn between two duties, household and nursing on one side, painting on the other". That same year, as Finland plunged into civil war, 10,000 Soviet soldiers were incarcerated in a camp on the edge of town where, deprived of food and fresh water, 3,000 would die within three months. But, as so often in her life, Schjerfbeck's thoughts were elsewhere, her mind directed inwards, her gaze fixed firmly on her canvas. There still exists a rare photograph of the camera-shy artist from that trip, standing at her easel in the town's park, a cloche hat on her head, a smile on her face, having a lovely time.
Seven years later, after the death of her mother, Schjerfbeck would leave Hyvinkää permanently for Tammisaari where, for the first time in her life, she had a place of her own. She was 63 years old. There she remained, painting prolifically, for the next 16 years. Today, she is treated as a local celebrity: the town has a museum that houses a collection of her works, a street named after her and a Café Schjerfbeck that serves Schjerfbeck cakes (topped with her monogram, drawn in chocolate), each place a stop on a guided tour led by her jolly doppelgänger.
During her life, this town was somewhat more ambivalent about its artist-in-residence; it is said she once offered the local wood-seller one of her more avant-garde paintings in lieu of payment and he scoffed: "What am I supposed to do with that, throw it on the fire?" Although her pioneering, personal brand of modernism – the paint applied directly on to untreated canvas, or scraped back using palette knives and sandpaper to create a rough-hewn finish – had already been feted in the Finnish capital and across the border in Sweden, Schjerfbeck was known in this former fishing village only as the reclusive lady with a limp who never married or had children, whose stick you could hear ricocheting off the cobblestones long before you saw her black dress bustle into view.
If her neighbours in Tammisaari were slow to catch on to Schjerfbeck's significance – she would be described in her obituary in Svenska Dagbladet (with a couple of qualifications that would no doubt have set her proto-feminist, cosmopolitan teeth on edge) as "not only one of the finest artists in her own country but the greatest woman painter of all time in the Nordic countries" – they were certainly not alone. The Royal Academy's exhibition is the first solo show of her work ever to be held in Britain. When you see its 65 portraits, landscapes and still lifes, a dazzling spectrum that stretches from an accomplished double profile in oils painted in 1881 when the artist was still a teenager, to a final, sombre composition of three pears on a plate, completed months before her death in Stockholm aged 83 – you'd be forgiven for wondering how such a singular talent has remained beneath our radar for so long.
"We're a bit behind the curve really," admits Sarah Lea, one of the Royal Academy's curators, before listing the countries where Schjerfbeck's work has been exhibited in recent years, among them France, Holland, Germany and Japan. "I think one of the reasons she hasn't been shown a lot here is because it is quite hard to classify or categorise her within the broader movements of art history. She developed her own very personal style."
You could say that Schjerfbeck became an artist by accident. At the age of three, she fell down the stairs at home and broke her left hip. Her mother underestimated the severity of her injury and failed to call the doctors; the delay in treatment left Schjerfbeck with a lifelong limp. Bed-bound during a prolonged convalescence, she was brought pencils and paper by her father (an office manager for the state railway who would die of tuberculosis when she was 13). She immediately demonstrated a prodigious talent for drawing that would, by the time she turned 11, earn her a scholarship to study at the Finnish Art Society in Helsinki, making her its youngest-ever student.
But it would be more accurate to say that Schjerfbeck was the author of her own destiny, her career shaped less by chance than by her indomitable ambition. Having won the painting prize every year at art school, in 1880 she was awarded a travel grant by the Finnish government in recognition of The Wounded Warrior in the Snow, her historical scene inspired by the Finnish War of 1808-09 that might have been tailor-made for the reactionary bureaucrats on the selection panel.
During the next 14 years, she travelled to the creative hotspots of Paris, Pont-Aven, St Ives, St Petersburg, Florence and Vienna – hungrily acquiring a deep understanding of the Old Masters and the emergent currents in contemporary art. She achieved commercial success during this period by pandering to the prevailing Victorian taste for sentimentalism: The Convalescent, a luminous oil of a flush-faced urchin painted in St Ives in 1888, was a shoo-in for the Paris Salon that year and remains one of the most popular works in the Ateneum national gallery in Helsinki.
But at the same time, she was honing her own style in more progressive works that she would not show in public for another 30 years, when modern tastes had begun to catch up with her. Lea suggests that you only need to look at The Door, her 1884 painting of sunlight leaking into the dark interior of a chapel near Pont-Aven, a picture that already seems to be straining against the limits of figuration, to see that "she wasn't going to be quite satisfied with the status quo".
These more adventurous works were not the only thing she kept from public view. In her early twenties, Schjerfbeck was engaged to a man known to posterity only as "the Englishman" (though it's now suspected that he was in fact Scandinavian). His identity remains uncertain not least because after he broke off the engagement by letter – citing misplaced concerns that her limp was evidence of a genetic predisposition to the TB that had killed her father – Schjerfbeck destroyed any correspondence that mentioned him, and demanded that all her friends do the same.
It is thought she later fell in love with Einar Reuter – the forester and painter who, having bought four of her works, came to visit her in the spring of 1915 when he was 34 and she 52 – although it's unclear if her feelings were reciprocated. Among the many arresting portraits on display at the Royal Academy, one stands out for its unabashed eroticism. The Sailor, for which Reuter posed topless in 1918 (the year after he'd written Schjerfbeck's biography) draws the eye irresistibly to a deep flush of red where his muscular neck meets his chiselled jawline. It reads like a heat-map of the artist's desire.
"Painting is more indiscreet than any other art," Schjerfbeck would write to Reuter the following year. "It is an incorruptible witness to the moral state of mind of the painter the moment he was holding the brush." Months later, Schjerfbeck paid for Reuter to take a holiday in Norway. He returned engaged to a woman 19 years his junior, who would, in due course, become his wife and the mother of his four children. As far as we know, Schjerfbeck never loved again.
Instead, she appears to have ploughed her passion back into her work. She was all but ignored by the establishment for most of the years she was holed up with her mother in Hyvinkää, a period during which she never once set foot in the Finnish capital and her unvarnished French-influenced style veered ever further from the kind of national mythmaking sought by the cultural arbiters of the new Finland. But in 1914 she became the only woman among nine artists commissioned by the Finnish Art Society to paint a self-portrait for the boardroom of the Ateneum. The result – her pale face offset by the fuchsia flash of her lips and a citric orange pot of brushes, a black background borrowed from the Old Masters scrubbed back in places to allow the canvas to peep through, her own name etched in distressed block letters above her head – still fizzes with modernity.
Over the next 15 years, under the shrewd guidance of Gösta Stenman – who paid her a monthly salary in exchange for being her sole gallerist – Schjerfbeck's reputation continued to grow, taking her, in 1939, to the brink of what would surely have been her international breakthrough, an exhibition of 120 works due to travel to the US. It never happened. When war broke out, the show was cancelled.
Yet if that blow derailed Schjerfbeck's career, if did nothing to staunch the remarkable flow of her art, which came increasingly to focus on the subject she knew best of all, herself. In the final 18 months of her life, by which time Stenman had persuaded her to move to the relative safety of a Swedish spa town, she completed more than 20 self-portraits, a series of unsettled and unsettling faces, in which the quietude of her earlier pictures is displaced by a febrile intensity. "She herself has not acquiesced to her fate nor is filled with peace," said the critic Sven Grönvall after visiting Schjerfbeck six months before her death. "She is no calm water."
The first of these late portraits (from spring 1944) appears to show the face of a woman who has just caught sight of death, her brow raised in shock, horrified mouth agape. By the last, no more than a few lines of charcoal committed to paper, that face has become a skull; the dying woman, death itself. A century on, these works retain such force that, as Lea says, they "feel like they could have been painted yesterday". It is as the creator of these extraordinary pictures, rather than as the jilted lover or the limping lady of Tammisaari, that Schjerfbeck deserves to be remembered.
Helene Schjerfbeck is at the Royal Academy, London W1 (royalacademy.org.uk), from July 20-Oct 27