Dancer Sergei Polunin has apologised to fans of the English National Ballet for disappearing just days before he was set to star in the premiere of Peter Schaufuss' Midnight Express in London, blaming a mystery "health issue" for his absence.

The Ukrainian star, 23, left executives frantic after failing to turn up for rehearsals in April (13), only to resurface in Moscow, Russia days later.

He was replaced by Johan Christensen in the lead role of imprisoned drug smuggler Billy Hayes for the show, and has only now addressed his decision to walk out of Midnight Express - although he has refused to reveal specific details.

Polunin says, "The only thing I can say is there was a health issue and I couldn't say anything at that time. I apologise to the audience because I couldn't even explain at that time... maybe one day I will."

He is now preparing to make his stage comeback in London in a production of the Moscow Stanislavsky Ballet's Coppelia this July (13), and he insists he is back in top form after focusing on his craft in Russia.

He adds, "I'm working well and dancing. I'm in good shape."