The Russian authorities are moving in for the kill in their pursuit of Yukos, the oil group, and its founder Mikhail Khodorkovsky. Last week's news that the tax office is claiming an extra $10bn in unpaid taxes, on top of the $7.5bn already sought, increases the financial pressure on Yukos to breaking point. Meanwhile, Mr Khodorkovsky's lawyer disclosed his client faced up to 25 years in prison if he were convicted of multiple frauds with which he is charged.

The next few weeks are crucial. Yukos has called an extraordinary general meeting for next month to consider filing for bankruptcy; the verdict in Mr Khodorkovsky's fraud case is expected in late January; in the meantime, Yukos shareholders are launching international legal action against the Russian authorities.