Mezzanine debt proved to be a surprisingly resilient asset class for European investors during the downturn, despite several lenders of the junior debt suffering high-profile write-offs, according to research.

European investors in mezzanine debt - which is one of the riskiest forms of debt as they bear early losses in the event of a default - suffered 11% fall in their investment between its peak in 2007 to its trough in 2009, according to a study by Swiss fund of funds Partners Group.