Grigory Sokolov is not yet a household name, but he should be. Many consider him, quite simply, the greatest pianist alive. He is 56, portly, his grey hair almost brushing his shoulders. He rarely announces his programmes as far in advance as most halls request; and he doesn't like interviews. It seems I'm the first British journalist to be admitted for a decade.
We talk, aided by a Russian interpreter, backstage in Barcelona after his recital at the Palau de la Musica Catalana. The concert began at 9pm and the stream of encores drew to a close at around 11.30pm. Now it's past midnight, but the pianist is still in performance mode. He's a polymath with a razor-sharp, immensely informed mind, and I am fortunate to catch him at his bubbliest. "Now it is still after the concert," he remarks, "but in three or four hours it will be the time before the next concert."
Sokolov was born in St Petersburg and still lives there. His first musical experiences occurred when he was too small to remember them: "I can only explain what I know from my parents. They understood that if I heard music in the street I stopped immediately and wanted to listen to it. At home, we had some records, I had a little podium and baton and I conducted everything that was there! Then they asked a piano teacher what to do with me. She told them: 'Wait until he is five years old and then start him to study piano'."
At 16, he won the Tchaikovsky international piano competition. But he remained virtually unknown in the West and, under the Soviet regime, his travelling was extremely restricted. After perestroika, that changed. Now he gives 80 concerts a year and fans snap up rare live CDs.
It seems unlikely that anyone has ever played like Sokolov before. His range of sound and colour seems unlimited: he's capable of the most delicate, jewel-like interpretations of French Baroque music but, in a work of superhuman power such as Prokofiev's Seventh Sonata, his massive sound can evoke a couple of symphony orchestras at full tilt. The piano is rarely in tune by the end of his recitals - he's even been known to break a string on occasion - yet his tone never descends into ugly bashing.
16 May (020-7638 8891; www.barbican.org.uk)