Investors decided months ago that Greece wasn't investment-grade: hence the €110bn ($134.45bn) eurozone and International Monetary Fund programme designed to replace market funding for at least two years. But bond market dynamics mean the cut may have serious repercussions.

The cut removes Greece from several major bond indexes, including Markit's iBoxx euro indexes, Barclays Global Aggregate and Citigroup's World Government Bond Index. These rely on either an average rating or having two investment-grade ratings.