The Climate Camp has come to Canary Wharf: Adair “Swampy” Turner says he’s “happy to consider” a tax on financial transactions if higher capital requirements don’t curb excessive profits and pay in the financial sector.

The so-called Tobin tax is the weapon of choice for those seeking to curb speculation and fund public goods such as international development and the fight against global warming. The endorsement of the idea by the Financial Services Authority’s chairman will incense many in the Square Mile. After all, until the credit crunch, Job One for City lobbyists was to win reduction or abolition of a different transaction tax – stamp duty on equities.