The credit crisis is widely held to have begun in July last year. That was when the market for debt instruments backed by subprime mortgages cracked, starting a chain of reactions that is still going on.

But for investment-grade non-financial companies, the true “crisis” did not start until three months ago – after the Lehman bankruptcy. At that point, their borrowing costs were barely any higher than they had been 15 months earlier. Since then, yields on BAA-rated bonds (investment grade) have risen by a third, according to Moody’s Investors Service, while yields on equivalent US Treasury bonds have dropped by a quarter.