Outgoing Bank of England policymaker Charlie Bean said on Sunday the bank could begin to unwind its quantitative easing programme of bond purchases once interest rates start to rise. "I think it will be natural either at the time the MPC (Monetary Policy Committee) raises bank rates, or sometime shortly thereafter to say 'Ok, we won't reinvest maturing gilts'," Bean, a deputy governor who leaves the bank at the end of June, told Sky television in an interview.