In the post-credit crunch era, when corporate default rates are rising fast, investors should perhaps be demanding more favourable terms than ever to buy the bonds of companies rated as sub-investment grade.

Not so, according to research by rating agency Moody's Investors Service on the European high-yield bond market, where covenant packages - designed to protect investors - have barely changed from those used at the height of the credit boom in 2006 and 2007.