One of Russia\'s biggest female ballet stars is leaving her full time job at a Saint Petersburg theatre to join London\'s Royal Ballet, in the latest of a string of convulsions to hit the Russian dance world. Natalia Osipova told a Russian newspaper Monday she had been given an offer she \"could not refuse\" to be a principal dancer at Covent Garden and would from now on only appear as a guest soloist at the Mikhailovsky Theatre in Saint Petersburg. Osipova and fellow ballet star Ivan Vasiliev, her partner on and off stage, had astonished critics in November 2011 when they quit the Bolshoi Theatre in Moscow for the far smaller Mikhailovsky. But now Osipova, regarded by some critics as the greatest Russian dancer currently performing, will be dancing full time at Covent Garden. To the surprise of many, Vasiliev will not be joining her. \"At the end I received an offer that I could not refuse,\" Osipova told the Kommersant daily in an interview, saying the decision was \"above all linked to the repertoire\" danced by the London company. \"I will now be a guest ballerina at the Mikhailovsky, we will break the five year contract (signed in November 2011) and agree another one,\" she added. The departure of Osipova and Vasiliev in 2011 from the Bolshoi -- where they had become its most bankable stars -- had already left the Moscow company reeling. It also heralded a ghastly period for the Bolshoi which culminated in an the acid attack on its director Sergei Filin, a crime over which leading dancer Pavel Dmitrichenko has now been accused. Osipova told Kommersant she did not expect she would see any repeat of the Bolshoi\'s notorious internal intrigues in London. \"In Britain all promises and conditions are put down on paper -- and not like what happens in Russia where everything is words. Working for this company (Covent Garden) is my desire and I want it with all my soul.\" Defections of Soviet ballet stars like Rudolf Nureyev or Mikhail Baryshnikov to the West became iconic moments of the Cold War. However now cultural tensions have calmed and one American star, David Hallberg, now even dances for the Bolshoi. Osipova has wowed critics with astonishing virtuosity in the great female roles of classical ballet, most recently on the Mikhailovsky\'s London tour which garnered five-star reviews. According to the Royal Ballet, her first performances as principal dancer will be as Juliet in Kenneth MacMillan\'s version of \"Romeo and Juliet\", partnered by the Cuban legend Carlos Acosta.