If you asked most people in the financial markets that question they would point to two things: another blow-up in the eurozone crisis, and the lurking fear that US budget policies are heading over a "fiscal cliff".

BBC: Gauging the fiscal cliff

But if the extraordinary events of the past day demonstrate anything, it is that investment banks are black boxes, and what really matters is not what sits in them but what their counterparties fear may be lurking inside.

ECONOMIST: Rescuing a Wall Street bank

Lurking behind all this is the fear that Virgin France and its bigger rival, the Fnac chain, will be wiped out by US multinationals who will come to dominate the French market.

BBC: French mourn Virgin's 'funeral march'