It's an old joke in London's capital markets that British Airways, the national carrier, is "a retirement scheme with a few aeroplanes attached", because its pension liability is about eight times the size of the company. Following Monday's 67% plunge in Royal Bank of Scotland's shares, the lender is in danger of becoming "a pension scheme with a small bank attached".

The Scottish bank, now 70% owned by the UK taxpayer, and its rival Lloyds Banking Group, have been the prime beneficiaries of state largesse. According to the latest available figures, these banks have in the region of £50bn (€53.9bn) of pensions obligations between them. RBS' schemes alone have liabilities of £27bn, six times its now much-reduced market capitalisation.