US insurer Nationwide Mutual has written down its investment in fund manager Gartmore by more than a third as a result of the equity bear market.

Nationwide paid about £1bn (€1.44bn) for Gartmore at the height of the boom in 2000, but at the end of 2002 reduced the value of its investment to £613m and took an impairment charge of £376m, according to Gartmore Group accounts filed at Companies House.