Central banks, net buyers of gold for the first time in a generation, are likely to retain their holdings even if they need to raise cash to counter an escalating debt crisis, according to Morgan Stanley. \"Once they\'ve sold, that\'s it, and buying back would be extremely expensive,\" said Peter Richardson, chief metals economist at Morgan Stanley Australia Ltd., who\'s studied metals markets for 20 years. \"They would rather have the backing of a rising asset within their reserve portfolios than use it to reduce debt.\" Gold rallied to a record this week as rising government debt burdens and weakening currencies boosted demand for a haven. Central banks are the biggest gold holders, and Thailand, South Korea, Kazakhstan, Mexico and Russia have added to reserves this year.