They wrote that policymakers, using an expanded European bailout fund, could end the Greek panic by offering to swap existing Greek bonds for newly issued bailout-fund debt at a steep discount.

The four shareholders have agreed to subscribe to and underwrite a share issue to enable Songbird to repay its entire debt to its lender, Citigroup, also a tenant in Canary Wharf, at a 5% discount.

The idea was that it could lend funds to Greece, which would buy back its debt at market prices-ie, at a deep discount to its par value.