American regulatory filings show that 35 foreign companies have delisted from American stock exchanges since April.

Rising costs, over-regulation and a culture of litigation have been cited as reasons for the exodus. In addition, US investors are preferring to buy stocks directly in overseas markets rather than from secondary listers in America.

British Airways, Danone and ICI have all described multiple accounting standards, lower trading volumes and near-draconian compliance under Sarbanes-Oxley law as reasons for turning away from secondary listings.

London is seen as the main beneficiary of this trend.