They are caused not by panicky human beings but by sophisticated (and unemotional) computer-generated algorithms that turn data into trades in milliseconds.

FORBES: Ignore The Noise Of High Frequency Trading

But the best way to regain its credentials is not to make a panicky move now but to hold its ground, tightening policy only when it is clear that the recovery can cope with the fiscal clampdown.

ECONOMIST: The inflation scare

The disproportionate punishment of Mr Flight and Mr Kruger, neither of whom have said anything that many Tories do not think, makes Mr Howard look more panicky than decisive.

ECONOMIST: Why one Howard's sacking is bad news for another

But if the ban is viewed as a panicky measure by eurozone authorities to provide temporary respite to financial institutions that are not as strong as they might be, then conventional investors in banks - and their creditors - would feel under greater pressure to remove their financial support from those banks.

BBC: Can a ban on speculation strengthen Europe's banks?