A lubricant retainer for use in a pump bearing assembly, the bearing assembly which in a first operating configuration is lubricated by a relatively highly viscous lubricant, and which in a second operating configuration is lubricated by a less-viscous lubricant, the bearing assembly comprising a bearing housing having a bore extending therethrough for receiving a pump drive shaft, spaced-apart bearing mounting zones within said bore with a chamber therebetween, each bearing mounting zone arranged for the in use receipt of a bearing therein. Each zone has associated therewith one lubricant retainer, the lubricant retainer being adapted to be mounted within the bore adjacent the bearing mounting zone with which it is associated so as to form a barrier between the bearing mounting zone and the chamber when the pump bearing assembly is in the first operating configuration, the retainer being removed when the pump bearing assembly is in the second operating configuration.