If the German Chancellor, Angela Merkel, keeps a portrait of Catherine the Great of Russia in her study, it is not, one hopes, because of the Russian Empress's expansionist foreign policy or the extravagance of her court, let alone the string of lovers she took.

It is because Catherine was a German and, more than that, a woman who worked and planned her way to the top and, having got there, used her wits and intelligence to stay and reign over Russia's age of splendour for a 34-year term.

Certainly, going around the splendid show mounted by the National Museum of Scotland from the holdings of the Hermitage Museum in St Petersburg, what impresses most - as it impressed her contemporaries - was how matronly she was.

As a visitor to the court wrote: "It was impossible not to be struck by her beauty and majestic bearing. She was a large woman who, in spite of being very stout, was neither disfigured by her size nor embarrassed by her movements."

There were portraits aplenty, most of them with the tiresome attributes of a neo-classical art that made play of symbolism and allegory - Catherine pointing to the tomb of Peter the Great to emphasise her debt to that ferocious tyrant; Catherine receiving the captured standards of the Turks whom Russia twice defeated in wars, and Catherine as Minerva, goddess of the arts.

But, at the centre of it all is a face of warmth and liveliness. There's a copy of a painting by Vladimir Borovikovsky (right), one the brightest young painters in the emerging Russian school of portraiture that she helped develop, of her walking in parkland at Tsarskoye Selo dressed in plain outdoor clothes, much like a figure from Jane Austen.

She rejected the painting as too informal but liked, and had copies made as gifts, of a head and shoulders by Mikhail Shibanov when she visited Crimea and the new territories conquered by her secret husband, the formidable Prince Grigory Potemkin. The portrait disguises nothing of her grey hair or her portliness but it is of a mature woman you'd love to meet and talk to.

She'd had a hard climb. Married at 16 to the heir to the Russian crown, Grand Duke Peter, she entered a loveless relationship in which both partners took lovers. She was there to provide an heir and, when she did, was thrust aside again.

As she recalled in her memoirs: "Finally toward noon, I bore a son ... the Empress Elizabeth had her confessor come and he gave the child the name Paul. The Empress immediately had the child taken to a midwife. No one had thought about me. I was dying of hunger and thirst. Finally, I was put in my bed and did not see a living soul the whole day."

The isolation lasted 17 years, during which she learned Russian, made friends, read widely and prepared for the day the Empress died. When it came, in 1761, she was ready.

Her husband lost support by being too much in awe of Russia's enemy, Frederick of Prussia. His German wife was seen as wholly Russian in her sympathies and her new Orthodox faith. Barely more than six months after he had become Emperor, Peter III was deposed and Catherine made Empress in 1762. A week later he died at the hands of the brother of Catherine's then lover, Count Grigory Orlov.

The show, on the 250th anniversary of Catherine's accession, calls her "Catherine the Great: an Enlightened Empress", which is pushing it a bit. Serfdom increased under her long reign as did the privileges of the nobility.

What she was, and what the Hermitage clearly glories in, was a German turned Russian nationalist determined to show that Russia, through patronage of the arts as much as conquest, was the equal of any in Europe.

Like a modern-day oligarch, Catherine had agents scour Europe for old masters and new commissions for her palaces and new arts foundations. Just as Peter the Great had done, she brought in architects, artists and artisans to glorify her court but also to teach the Russians to produce the same.

Porcelain, tapestry work, gemstones and ironwork, all found themselves encouraged with new factories and an assured imperial market.

Rational as she was, she preferred the new neo-classicism to the old Baroque or, in later life, to the new Romanticism.

She had no ear for music, no discernible taste of her own in commissioning pictures. But she was passionate about architecture and interior decoration. Building, she declared, was a "diabolical thing. The more one builds the more one wants to build, it is as intoxicating as drink."

She managed men as Elizabeth I of England had done: with care and to purpose. She balanced the forces of the country with great skill and she brought up her grandchildren with fondness.

She was known as "mamuschka" or "little mother" in Russia, just as Chancellor Merkel is called "mutti" or "mum" in Germany today.

- Independent