Who would want to kill Yegor Gaidar? He played the central role in reforming Russia's moribund economy in the early 1990s, but is not a particularly active figure in politics today.

Many blamed Mr Gaidar's "shock therapy" for the slump that cast millions into unemployment and wiped out their savings, but there has been no suggestion of any recent threat to his life.

The economist has largely withdrawn from politics to concentrate on research at the think tank he heads in Moscow. His new book, Downfall of the Empire: Lessons for Modern Russia, was well received but not seen as presaging any return to the political arena.

Mr Gaidar, 50, is critical of President Vladimir Putin's efforts to restore state control over large areas of the economy. But nobody regards him as implacably hostile to the Kremlin in the manner of the murdered journalist Anna Politkovskaya or the former FSB agent Alexander Litvinenko.

A week before he was taken ill, Mr Gaidar told an audience at the American Enterprise Institute in Washington, DC that Mr Putin's economic and foreign policies had been better than he had feared initially.

But he added: "On the democracy, he was much worse than I ever predicted."
His daughter Maria is a prominent member of a liberal youth group and staged a protest last week in which she and a fellow activist unfurled a banner from a bridge near the Kremlin that read: ""Return the Elections to the People, Bastards!"

Even so, Mr Gaidar's friends have not pointed the finger of suspicion at the Kremlin over his poisoning. Rather, some have suggested that it is part of a larger conspiracy to discredit Mr Putin by attacking liberal critics ahead of elections in 2008.

Mr Putin has made clear that he will abide by the Constitution, which bars him from seeking a third term of office. Potential successors are already jostling for advantage and the fear in many quarters is that the struggle for power is turning vicious.

The air in Moscow is rife with talk of conspiracies involving any combination of exiled oligarchs, rogue secret agents, devious Western powers, and Kremlin powerbrokers. With a dearth of hard facts, the ones people favour are largely determined by their prejudices.

What is undoubted is the sense of uncertainty that now pervades the political environment in the wake of Mr Gaidar's illness. Nobody is sure what is going on, but everyone is convinced that it is far from over.