Johnny Stuart, who has died aged 63, had no equal outside Russia as an expert on Russian art. The thriving market in Russian art today is largely his creation. He founded the Russian department at Sotheby's in 1976 and over the next 20 years built it up into a dominant position that was reflected in Sotheby's record-breaking Russian sale of 1995. No aspect of his field left him indifferent. Aside from his principal interest in icons, he was equally fascinated with Russian painting of the 18th, 19th and 20th centuries, as well as with porcelain and objets d'art. His book Ikons, published by Faber & Faber in 1975, remains the most accessible general work on the subject.
Stuart later undertook a far more ambitious and in-depth project, and shortly before his recent illness, after 20 years of study, he had completed the manuscript for Icons: The Triumph of Orthodoxy, a huge, comprehensive volume which is soon to be published by Alexandria Press.
Yet to describe Stuart as an art historian in the modern, professional sense did not begin to describe him. He belonged firmly in the great 18th-century British tradition of gentlemen eccentrics, polymaths and connoisseurs. He blended high scholarship with a plethora of interests in history, genealogy, interior design, pop culture and the Rocker scene of the 1960s.
For work at Sotheby's he habitually wore motorcycle leathers, and he cut a dash turning up for valuations on one of his classic bikes.
His book Rockers (1987), about the English bike scene of the 1960s and 1970s, became an international bestseller and for a time was reputedly the most shop-lifted book in London bookshops; it continues to do brisk trade in Japan.
John Spencer Innes Stuart was born in Aberdeen on May 20 1940 and grew up in Angus, where his father farmed after the Second World War. Johnny loved drawing, and at Eton, encouraged and influenced by Wilfrid Blunt, his art master, he sought to learn about the Italian Renaissance, Persian painting, and Chinese art. While still at school he would go up to London to rummage in the salerooms, where among other things he acquired a pair of Chinese ceremonial brass fans, described in the catalogue as having been looted by a British officer during the sack of the summer palace in Peking.
Around this time, Stuart also began to show a keen interest in Roman Catholicism. His parents, alarmed at this development, asked his housemaster, G A D Tait, to do what he could to distract him, and so it was that he was given a book about the Russian Imperial Family. From there developed the great passion of Johnny Stuart's life. He immersed himself in Russia's history, culture and art, and became firm friends with the Russian émigrés Count and Countess Kleinmichel, who stood as his godparents when, while still at Eton, he converted to Orthodoxy.
Stuart went on to develop these interests at St John's, Cambridge, where he read Slavonic Studies under Professor Andreyev, a follower of the leading early Byzantinist, N P Kondakov. In his holidays he moved in Russian émigré circles, and avidly sought to learn about the closing days of the Russian empire.
After Cambridge, Stuart based himself in Notting Hill. His homes, first in Kensington Park Gardens and then in Colville Mews - a former industrial warehouse converted into a Russian neo-classical palazetto - became meeting places for people of vastly different backgrounds and interests.
In 1963 he was engaged by Peter Wilson as a porter in the porcelain department of Sotheby's, quickly moving to be an assistant in the Russian section of the Works of Art department. The great collector of Russian Art, George Kostaki, remarked to Wilson that his porter seemed to know far more than the expert in charge.
Stuart's restless and curious nature soon led him to leave Sotheby's to go into partnership with Marina Bowater at the Bowater Gallery, then a meeting place of the Russian diaspora in London. But he found running a gallery too limiting, and in the late 1960s he went to Russia to study under Adolf Ovchinnikov at the Grabar Centre for Icon Research and Restoration in Moscow. Helped by his great friend Camilla Gray, who was married to Sergei Prokofiev's son, the painter Oleg, Stuart made lifelong friends among the Russian artistic and scholarly intelligentsia.
It was to be the first of many visits, and it is fair to say that Russia became his second home.
The process was repeated a few years later, in the early 1970s, this time in Greece. Through another great friend and distant relative, Elmina Rangabe, he spent a year there immersing himself in its Byzantine heritage and the roots of Christian art.
When he returned to Sotheby's in 1976, he managed to persuade his superiors of the need for a separate Russian department, which he then headed for the next two decades, while also doing the research for his second book on icons. His understanding of icons included a formal appreciation of them as art and a knowledge of the theology behind them. More important, it stemmed from his Orthodox faith and his complete communion with the world that gave them birth. He always insisted that the aesthetics of religious art could only be appreciated by understanding the spiritual tradition that produced it.
Ever ready to discuss Patristic theology and the finer points of the Christological disputes of the 4th century, he was, though, equally keen to share his enthusiasm for classic British motorcycles. His passion for large and powerful motorcycles dated back to his schooldays. Not a day went by when he did not ride his bike and over the years he was the proud owner of several classic machines, ranging from a 1935 Thunderbird, via Nortons and Tritons to the latest model Triumph. Meanwhile, his understanding of youth culture, his enjoyment of the glamour of the music scene, and his knowledge of street style and fashion made him a guru for actors and pop stars.
Among those he influenced and befriended were members of the Rolling Stones, Oliver Tobias, Zandra Rhodes, George Michael, Spandau Ballet, Gary Numan, Steve Strange, Duran-Duran, Billy Idol, Brian Setzer of the Stray Cats, Paul Simonon of the Clash, Huggi, and Kylie Minogue.
The makers of films and pop videos came to him for advice on matters of style, and when the V & A held an exhibition on British Street Style, they called on him for help in styling the show and to lend motorcycles, original bikers' clothing, accessories and memorabilia from the 1950s and 1960s.
Stuart left Sotheby's shortly after the Russian sale of December 1995 and formed an art consultancy with his former colleague Ivan Samarine, advising collectors and dealers throughout the world. Entrusted with their treasures, Stuart's home became an ever-changing showcase of Russian art.
In recent years he fulfilled a long-held ambition - the culmination of years of absorbing the minutiae of Russian style - by renovating a large derelict apartment in the heart of St Petersburg on the Fontanka river, in the house where Turgenev once lived, and turning it into a splendid early 19th-century Russian palatial residence. Featured in Russian Vogue, along with photographs of his home in London, it led to other commissions in Moscow.
Johnny Stuart was handsome, charming, self-deprecating, and an excellent host. His hospitality combined with his wide-ranging interests gave his soirees the character of a salon. A great raconteur, he was forever regaling his friends with wonderfully funny stories, and could spend hours discussing the finer points of style, interior design and architecture. Byzantium, Russian neo-classicism, the Ottoman world and Fifties Britain were his favourite styles - a synthesis reflected in his own homes.
Fascinated by languages and their sounds, he spoke fluent Italian, French and Russian. Even in languages such as Greek and Spanish, his knowledge of which was far more limited, his talent for mimicry often confused natives into thinking him one of their own. Gifted with a great ear, he could render exactly the accent or vocal mannerisms of his interlocutors, always to their great merriment.
He had the rare ability to communicate across generations and social classes. A bachelor, he was a highly popular uncle and godfather.
He died on July 12.
John Stuart Scholar of icon painting and expert on Russian history
22 July 2003