Investment trust RIT Capital Partners said net asset value fell in the half year to September 30th as some of its defensive hedges under performed in a rising market.NAV per share fell 4.9% to 1,188.1p in the six-month period from 1,249.3p at the end of March. Net assets fell to £1.8bn from £1.9bn six months earlier, representing a decrease of £77.9m. "Some half of the decline was accounted for by some of our defensive hedges moving against us in a rising market. The other negative factor was underperformance by a few externally managed portfolios. We have taken active steps to address this," the group explained.Chairman Lord Rothschild added: "We intend to focus our investments on such individual situations and on external managers who recognise the new realities. Over time we are confident that this concentration, together with relentless attention to detail on all our investments, will see us outperform markets."The group, which has changed to a December year-end, from a March year-end previously, will next report for the nine months ended December 31st 2012; thereafter we will be on a calendar year cycle.An interim dividend of 28p will be paid for shareholders on the register at June 15th up sharply from a 4p payment at the end of March. CJ