Royal Bank of Scotland has always struggled to explain why it believes it necessary to own the 16th-largest bank in the US by assets. Regulators have been pressuring the 81% UK government-owned bank for months to sell RBS Citizens Financial, the New England-based lender, to boost its domestic capital ratios.

Now RBS appears ready to concede the point, with the board debating whether to commit to float a stake of up to 25% within two years. But that is unlikely to make much difference to the bank's fortunes.