A heat storage and transfer system that incorporates a primary heat storage chamber or body that is thermally insulated and which in use contains a heat storing liquid or solid; and a secondary chamber external to and adjacent the primary heat storage chamber or body through which a liquid, heat transfer fluid or steam to be heated is passed in use, the system having a heat transfer mechanism to selectively transfer thermal energy from the heat storing liquid or solid of the primary heating chamber or body to the liquid or steam to be heated in the secondary chamber. The heat transfer mechanism has a drive that moves the secondary chamber from a first position that is thermally separated from the primary chamber into a second position that is substantially inserted in a void or recess within the primary chamber or body.