They are two of the biggest names in world opera and ballet, with pedigrees stretching back to the days of Catherine the Great and the Russian empire. And this summer the British public will get the chance to make a direct comparison of the Mariinsky (formerly the Kirov) and Bolshoi companies as they go head to head on the London stage in an astonishing clash of the titans.
The Bolshoi begins a month-long residency at the Royal Opera House on 25 July with the first-ever visit of its opera company to Covent Garden, followed by a season of performances by its ballet company. This is the 50th anniversary of its first appearance in London, and interest was expected to be high.
But Russian fever heightened further yesterday when it was announced that the Mariinsky Theatre will also undertake a London residency in July, with performances of both opera and ballet at the London Coliseum starting five days earlier.
For fans, there was both delight and surprise at what could prove an expensive summer for those eager to catch not only two world-class companies, but some new and rare repertory. And although all parties are trying to play down the element of competition between the two great Russian ensembles, it is clear that comparisons will be made.
Valery Gergiev, the charismatic artistic director of the Mariinsky (which was renamed Kirov by Joseph Stalin and has since reverted to its historic name), managed to step up the tension even while trying to insist there was none when he spoke from New York yesterday. "I hope that both companies will be successful. I think we do not have a sense of rivalry or competition, though maybe it looks like that on paper - two famous companies trying to out-do each other," he said.
"I've been responsible for the Mariinsky for nearly 18 years. The Bolshoi has changed maybe three or four or five times in the leadership position. Maybe that's a good thing ... but it feels we have much more stability.
"I wouldn't comment on the quality. I think you can see it for yourself. But we make a lot more recordings with the symphony orchestra, we play maybe 10 concerts against every single concert that the Bolshoi plays and we play regularly at the Carnegie Hall and the Barbican. Maybe it's not that we say we're better, it's a totally different structure."
Music and ballet-lovers will be champing at the bit to see both. Zoe Anderson, dance critic of The Independent, said she was genuinely excited because the companies were not normally in the same place at the same time.
"They don't usually go head to head and balletomanes like to compare and contrast. But it's also exciting because they are both doing unusual repertory."
The Mariinsky residency announced yesterday will be called Shostakovich on Stage. It will include highlights of the company's celebration of the centenary of the birth of Dmitri Shostakovich which will be presented in May and June at its Stars of the White Nights festival in St Petersburg.
There is the chance to see works the company has never presented in Britain before, including the Shostakovich operas The Nose, based on a satirical story by Gogol, and Katerina Izmaylova, a revision of his earlier opera, Lady Macbeth of Mtsensk. There will also be the ballet version of his Leningrad Symphony and his ballet, The Golden Age, which is a new staging especially for the centenary year.
The Bolshoi season, too, includes three new works, including a new version of Prokofiev's ballet Cinderella and, continuing the Shostakovich theme, the first British performances of his ballet The Bright Stream, which was banned by Stalin in the 1930s but, now revived, has attracted rave reviews in Paris and New York.
The opera programme will include the Bolshoi's celebrated production of Mussorgsky's Boris Godunov at Covent Garden for the first time.
Lilian Hochhauser, the promoter who has been bringing Russian stars to the UK for half a century and is presenting the Bolshoi this summer, is obviously slightly disappointed there will now be a clash. "It's not a question of concern about the clashes but it's a pity one can't savour the companies separately. All of these artists are at the height of excellence. They are top of the league. It seems strange that it should happen."
She notes, sadly, that five years ago when she was bringing the Mariinsky, she courteously dropped its production of Lady Macbeth from the programme because the English National Opera was presenting its own. She questions the wisdom of having The Nose at the Coliseum and at the Linbury Studio of the Royal Opera House at virtually the same time.
And she defends the "immensely strong and rich repertoire" of the Bolshoi. They had always had "a great resonance," she said. " We first brought the Bolshoi over in 1963. Subtly, things change, but they have never lost their bravura, they're still a very dashing company."
But she is also generous about the rival programme - not least because Shostakovich was a personal friend until his death in 1975. "He was a genius and he deserves it," she said. "He was a very nice and gentle man to talk to. He had a great deal of turmoil going on in his life, he was obviously under great stress [working under the Communist government], but he was never less than polite."
Valery Gergiev said the Mariinsky would probably have been at the Royal Opera House with the Hochhausers had they wanted to return to London for "another season of traditional repertoire". But he said: "I do not believe this is what London expects or wants from the Mariinsky. I think we should not do another seven Swan Lake performances or four Bayadères. We can do it very well, everyone knows, but that is not what I wanted."
British audiences were already responding warmly to the cycle of Shostakovich symphonies he has been conducting at the Barbican Centre in London and he believed they would be interested in the work the Mariinsky was preparing for the Shostakovich centenary - namely, all the great Russian composer's works for the stage. "Unquestionably Lady Macbeth and its second version, Katerina Izmaylova, are gigantic, impressive works for the theatre. Then there is The Nose, a very provocative opera, a very important step for a young man. Then there are an number of ballets that show his contribution to the progress of opera and ballet as a genre," Gergiev said.
"Visitors will maybe go to see Swan Lake [with the Bolshoi] but maybe those who are curious and experienced and want interesting presentations will be ready for Shostakovich evenings in London."
John Allison, editor of Opera magazine, said the buzz in opera circles had been around Gergiev and the Mariinsky in recent years - not least because their hectic programme made them seem to be everywhere. "It's interesting. I'm sure people will make comparisons and I'm not sure whether that will favour either in the end," he said.
"Historically for a long time, the Bolshoi was perceived as being the greater company but when Gergiev came in he reinvigorated [the Mariinsky]. It is perceived as having the upper hand over the Bolshoi. If you had to say which company was stronger, I would say the Mariinsky without a doubt, but that is not to dismiss the Bolshoi in any way. They do lots of interesting work and the Mariinsky does some quite duff work."
The Bolshoi production of Prokofiev's opera The Fiery Angel directed by the international superstar Francesca Zambello took Moscow by storm, for instance, when it was performed for the first time two years ago (it was never performed during the composer's lifetime). Covent Garden has previously presented the Mariinsky's own acclaimed production of the opera. "They really are going head to head," Allison said. "But I think it's good news. I'm sure the critics will be happy to have them both here at the same time. Competition is very seldom a bad thing."
Zoe Anderson said that what dance-lovers would be comparing was partly a matter of the two companies' respective styles. "Historically, the Bolshoi had a reputation for big, heroic, passionate dancing, while the Mariinsky were elegant, lyrical, refined," she said.
But some of these differences were less pronounced today, she feels. " They were both Soviet state flagships and therefore until the end of the 1980s they were well-funded and well-looked-after. They have both had a tough time since and both have had to adjust - including taking on Western repertory," she said.
The repertoire from the Mariinsky was a surprise, Anderson said. "I wasn't expecting to see this repertoire from them and the Shostakovich theme is interesting. This is a bonanza for Shostakovich fans. There are works that are being resurrected, while the Bolshoi is showing a new Shostakovich ballet."
Ticket prices for the Shostakovich on Stage season at the Coliseum will range from £15 to £80 for ballet performances and £18 to £115 for opera. It was "clearly a non-commercial project," Gergiev said. To go ahead with the season, the Mariinsky has needed backing from the Russian Federation government, the foundation of the pools philanthropist Peter Moores and the Mariinsky Theatre Trust, whose 1,000 members have been supporting the company's work since 1993.
Caroline Gonzalez-Pintado, the Theatre Trust's chief executive, said: " The idea was really Gergiev's baby, we're just very pleased to be able to make it a reality." She added: "I don't think there will be an evening when the Mariinsky ballet is on stage at the same time as the Bolshoi ballet is on stage. I think there will be ballet at one [venue] and opera at the other. It's just a wonderful chance to see so much Shostakovich which we very rarely have the opportunity to see. UK audiences are going to be in for a real feast."
1776: Founded in Moscow by Michael Maddox, an English entrepreneur, and Prince Urusov, a patron of the arts
1806: taken over by the Imperial government
1825: The present 2,000-seat Bolshoi Theatre opens. Permieres of Glinka's Ivan Susanin and Ruslan and Ludmila in the 1840s mark the birth of a truly Russian school of composition
1877: First performance of Swan Lake, originally a failure but now a much-loved favourite
1917: Left-wing critics demand the removal of "bourgeois" composers such as Tchaikovsky from the repertory but moderate voices prevail
1920s: Bolshoi Theatre gives free concerts for soldiers and workers
2005: Reconstruction of the main Bolshoi Theatre stage begin, with performances only on its New Stage
2007-2008: Performances on both stages will restart
Mariinsky Theatre (formerly the Kirov)
1740s: First Russian ballet company is set up in St Petersburg, laying the foundation for what becomes the Mariinsky
1783: Catherine the Great establishes an official home for the Imperial Italian Opera
1860: New theatre for the Russian troupe opens, named Mariinsky after the Empress Marie who ordered it
1862: Verdi's La Forza del Destino receives its premiere
1935: The Mariinsky is renamed the Kirov by order of Soviet leader Joseph Stalin in honour of Sergey Kirov, a Communist leader whose assassination the previous year marked the beginning of the Great Purge
2003: Dominique Perrault wins an architecture competition to design a new building for the theatre, which will sit alongside the old
2006: The Mariinsky Theatre closes for refurbishment