Ian,
Try this - sand it back but do not polish it. Get a chinese take away plastic tub with lid or similar. Get some ammonia, 80/80 is best and very acrid but household ammonia can work. Put some of the ammonia in the take away tray and suspend the turned wood in the tray and secure the lid, all without breathing! Preferably so it outside. Put it where you can see it and check on it to see how it darkens. Damp or freshly dried will be high in Tannin which will react with the Ammonia, really dry oak will need time, could be as much as a week. When done take it out and leave it for a while to defumegate and them polish on the lathe.