Given the uncertainty surrounding UK banking regulation, it is hardly surprising leading international banks based in London are toying with the idea of shifting headquarters. At Barclays, the planning already is far advanced.

The bank is undertaking detailed analysis of likely regulatory hurdles to switching its domicile to New York and has had preliminary conversations with US regulatory officials, says a person involved in the process. It estimates the cost of a switch at "several hundreds of millions of pounds" in addition to the £30m ($48m) it expects to spend on preparatory work. No decision is expected until at least September, after the direction of UK financial regulation is clearer and key elements of the US Dodd-Frank financial-overhaul bill have been clarified.