Theatre administrator and former deputy director of the Edinburgh Festival;

Born: May 4, 1934; Died December 30, 2012.

Count Alexander Schouvaloff, who has died aged 78, was for several years Peter Diamand's suave, dark-haired, expert, quietly watchful and faintly secretive deputy director at the Edinburgh International Festival, having briefly held the same post under Lord Harewood before assembling a major Diaghilev exhibition (entitled Parade, in tribute to Erik Satie's ballet of that name) at Edinburgh College of Art for Diamand's successor, Sir John Drummond.

Alex, as we used to know him in Scotland, was a world authority on Diaghilev, whose knowledge was sought wherever he went and whose ability to surmount obstacles was employed with invariably soft politeness – Who's Who listed his principal hobby as "skating on thin ice". Lord Harewood, in his memoirs, called him a man of the theatre who was prepared to face making decisions – even unpleasant ones – on his own.

After Lord Harewood's resignation, he was responsible for the Edinburgh Festival's productions of The Trojan Women with Flora Robson and Cleo Laine and the Prospect Company's Cherry Orchard with the distinguished Lila Kedrova as one of its stars. After Diamand's departure came the comprehensive Diaghilev exhibition, which was so successful that it moved to the Victoria and Albert in London.

Born into the Russian aristocracy, he was educated at Harrow, where he played the lead in a production of Hamlet, and at Jesus College, Oxford, before becoming a military policeman at the Supreme Headquarters Allied Powers Europe in Paris – though the writer of this obituary, who did his National Service in the same international organisation at the same time, never knowingly encountered him.

Theatre was not only in his blood but also that of his ancestors. His father received an Oscar for his spectacular designs for Moulin Rouge, John Huston's vivid 1952 film starring Jose Ferrer as Toulouse Lautrec. His great-uncle, Prince Abamelek-Lazarev, owned a villa in Rome which he bequeathed to "the Tsar and the Russian people" with the aim of transforming it into a Russian Academy, but his desire was never fulfilled.

In 1974, side by side with his Edinburgh duties, he became curator of the V&A's Theatre Museum, which naturally had an emphasis on Diaghilev and made use of material from Richard Buckle's famous Edinburgh Festival exhibition in 1954 before it transferred to London. He also directed North-West Arts in the north of England for seven years, encouraging Northern Dance and the Royal Northern College of Music in Manchester, as well as many smaller organisations. When, eventually, he founded the Theatre Museum on the piazza at Covent Garden, opened by Princess Margaret in 1987, the achievements of Diaghilev were again an important presence.

Though he called it "a collection of collections", and though he should have been the ideal choice for the appointment, the premises – earlier those of a fruiterer – were deemed somewhat cramped and his traditional good relations with colleagues on this occasion came to grief. His friendship with Sir Roy Strong, director of the V&A, and with Sir Roy's successor developed into rivalry, as perhaps it was bound to do, and he resigned in 1989. The museum continued until 2007, when it was closed for lack of cash. New galleries of the performing arts were opened at the V&A two years later.

But Count Schouvaloff (his surname pronounced with the accent on the letter "a") seemed undeterred by such mishaps. Until he was 73, he was a long-serving trustee of the London Archives of the Dance, and his expertise took him around the world, advising on important exhibitions and writing fine catalogues for them. Among his numerous books are Stravinsky On Stage, Leon Bakst – The Theatre Art and The Art of Ballets Russes, published by Yale University Press in association with the Wadsworth Athenaeum in Connecticut. He was married twice – firstly to Gillian Baker, with whom he had a son. His second wife Daria, whom he married in 1971, survives him.