Ever since the 50 per cent windfall tax on bankers' bonuses was announced, a chorus of high-pitched noises - the words "stuck" and "pig" come to mind - has been coming out of the City and its adjuncts, from hedge-fund-friendly Mayfair to Canary Wharf. It warns the rest of us that such vindictive action will drive entrepreneurial talent out of the country and bring about the downfall of London as the world's pre-eminent financial centre.
The hedge funds and wealth managers are threatening to decamp to Geneva or Grand Cayman, dealer-brokers to Zurich or Zug. They argue that they can run their global businesses just as effectively out of such low-tax havens. The only loser will be UK plc, both in terms of forgone tax revenues and the international standing of the City of London.
Some of this noise is directed internally to persuade big-revenue earners not to jump ship. For, during a year when banks have benefited from cheap money, public guarantees and rising markets across all asset classes, it has been difficult not to make money hand over fist. Headhunters have not been idle. There has been much poaching of the seriously big hitters.
Raising the possibility of moving to a low-tax jurisdiction is one way of keeping the bonus-hungry on board, alongside avoidance measures, such as substituting salary hikes for year-end bonuses, deferred payments or contracts for difference.
The Treasury's estimates of how much revenue will be raised by bonus-bashing may nor may not be exaggerated. But so, too, are the dire warnings of how the tax will undermine the attractions of London as a financial centre. Some hedge funds may indeed leave. But the big banks and fund managers need to stay close to their clients. Moreover, they rely on the legions of ace City-based lawyers, accountants and information and communication technologies specialists to keep their businesses running and to be more or less tax-efficient.
A one-off windfall tax will not drive them out, especially now that France and other countries have indicated they will follow suit. It is a temporary measure, designed to encourage banks to channel the windfall profits they have made on the back of public money towards rebuilding their capital base, rather than dispersing it among already highly paid employees.
What might persuade global banks to shift more of their operations away from London would be a permanent tax regime that placed them at a disadvantage to other financial centres. The hope is that there will be co-ordinated action by G20 members to prevent such taxation-driven migrations.
The real challenge to the City comes from other developments in the world economy - the relentless rise of China and the other big emerging economies - not just in terms of production but as the new seats of capital. Global banks like to be close to the centres of both capital accumulation and investment. These days, those are overwhelmingly in the east.
Last year, Hong Kong handled more than twice the value of initial public stock offerings in either London or New York. When HSBC decided to move its chief executive, Michael Geoghegan, from London to Hong Kong, it was for long-term strategic reasons, not for tax reasons. Over time, the City may become just one of a constellation of financial centres. But it will not lose its attractions simply because of a one-off tax.
This article is taken from the New Statesman supplement Held To Account: What's next for UK Banking? sponsored by Barclays